Chapter 33 Recurrent Pregnancy Loss
KEY POINTS
1 Isolated spontaneous pregnancy loss is common and approximately 15% to 30% of recognized pregnancies end in miscarriage. Recurrent pregnancy loss defined by three or more miscarriages is rare, occurring in 1% of women.
2 Clinical evaluation of a couple with recurrent miscarriage is warranted after two miscarriages caused by similar prevalence of abnormal results for couples with two or three pregnancy losses.
3 The most common cause of first trimester miscarriage is fetal aneuploidy.
4 Evaluation of patients with recurrent miscarriage should include a detailed patient and family history and examination of anatomic, genetic, endocrine, and antiphospholipid syndrome abnormities.
5 Much of the traditionally accepted testing, such as thrombophilia screening and several immunologic screening tests, are not supported by current evidence.
6 At least 50% of couples will have no specific abnormal finding after an evaluation for recurrent miscarriage.
7 After several pregnancy losses, there remains a greater chance of having a viable birth than another miscarriage, even without treatment. Prognosis can improve with treatment of a known underlying etiology.
8 Controversial treatments for recurrent miscarriage, including in vitro fertilization with chromosomal screening of embryos, immunosuppression, and anticoagulation, remain under investigation.
9 Treatment for recurrent pregnancy loss should include close monitoring with β- human chorionic gonadotropin levels and ultrasound, psychological support, and karyotypic analysis of tissues from subsequent miscarriage.
Despite advances in research and technology, recurrent pregnancy loss remains a clinical and emotional challenge for patients and providers. Sporadic miscarriage is the most common complication of pregnancy affecting approximately 1 in 4 couples in their reproductive years. Approximately 70% of human conceptions fail to achieve viability, and an estimated 50% are lost before the first missed menstrual period (1). Studies using sensitive assays for human chorionic 1961gonadotropin (hCG) indicate that the actual rate of pregnancy loss after implantation is 31% (2). [1] Miscarriage occurs in 15% to 25% of pregnancies that are clinically recognized before 20 weeks of gestation from last menstrual period (3,4). Traditionally, recurrent miscarriage has been defined as the occurrence of three or more clinically recognized (ultrasound or histopathologic evidence) pregnancy losses before 20 weeks from the last menstrual period (5).
Using this definition, recurrent pregnancy loss occurs in approximately 1 in 300 pregnancies (2) and in less than 1% of women (337). [2] Clinical investigation of pregnancy loss, however, may be initiated after two consecutive spontaneous miscarriages (338). A study of more than 1,000 patients with recurrent pregnancy loss reported no difference in the prevalence of abnormal results for evidence-based and investigative diagnostic tests when the diagnostic workup was initiated after two versus three or more losses (6). If clinical intervention is undertaken in the form of investigation after two spontaneous miscarriages, approximately 1% of pregnant women will require evaluation (3). Even with a history of recurrent pregnancy loss, a patient is more likely to carry her next pregnancy successfully to term than to miscarry. For patients with a history of recurrent pregnancy loss, the risk of subsequent pregnancy loss is estimated to be 24% after two clinically recognized losses, 30% after three losses, and 40% to 50% after four losses (7). These data make clinical study of recurrent pregnancy loss and its treatment difficult because very large groups of patients must be studied to demonstrate the effects of any proposed therapeutic intervention.
ETIOLOGY
Recurrent pregnancy loss has been attributed to genetic, anatomic, immunologic, endocrine, thrombophilic, and infectious causes but etiology remains under investigation. [6] Although the exact proportion of patients diagnosed with a particular abnormality varies by study, parental genetic abnormalities (2% to 5%), anatomic issues (10% to 12%), antiphospholipid syndrome (APS) (15%), and other identifiable issues (10%) have been found in couples with recurrent miscarriage. This leaves approximately 50% of couples with a diagnosis of unexplained recurrent miscarriage (Table 33-1) (3,6,8,338). The lack of abnormal findings in the couple having recurrent pregnancy loss is not surprising given how common fetal aneuploidy is with conception.
[3] At least 60% of preclinical and early clinical pregnancy losses are the result of de novo fetal aneuploidy (9). Among women aged 35 or greater who experience recurrent pregnancy loss, spontaneous fetal chromosomal abnormalities are responsible for over 80% of losses (10). This is thought to be the cause of anembryonic pregnancy losses, whereas pregnancy losses occurring after 10 weeks of fetal development are much less likely to derive from fetal aneuploidy. Pregnancy losses resulting from de novo fetal aneuploidy, whether early and undocumented or documented through evaluation of chromosomal content in fetal tissues, cloud the results of many published studies. Their presence or absence must be documented in all investigations on recurrent pregnancy loss patients and their potential as a confounding factor discussed. The timing of fetal demise and tissue chromosomal analysis of any collected fetal tissues should be carefully weighed when diagnostic and therapeutic investigations into causes of recurrent pregnancy loss are being considered.
Genetic Factors
Approximately 3% to 5% of recurrent pregnancy loss can be associated with a parental balanced structural chromosome rearrangement and can be diagnosed with blood tests for karyotype for both partners (338). Chromosome rearrangements are most commonly balanced reciprocal but can include robertsonian translocations, chromosomal inversions, insertions, and mosaicism (11–14). A balanced reciprocal translocation is a rearrangement in chromosomes in which breaks occur in two different chromosomes and the pieces are exchanged so that no genetic material is lost or gained in the process. Balanced rearrangements can only be detected with standard G-banding karyotype. Highdensity microarray technology and next-generation sequencing can detect smaller deletions and duplications, but are not able to differentiate balanced rearrangements from normal because the total genetic content is the same. When screening parents for chromosome rearrangement, the best test is a metaphase karyotype with G-banding. Embryos from a parent with a balanced translocation with a normal phenotype have either two normal chromosomes or inherit the balanced translocation; however, some embryos can have abnormal chromosome content and lead to babies born with birth defects if they inherit an unbalanced translocation. A robertsonian translocation is a form of chromosomal rearrangement with one of the short-arm chromosomes (13–15) in which there is a loss of part or all of the short arms and fusion of the long arms of the chromosomes. A balanced robertsonian translocation causes no health issues but unbalanced forms can result in trisomies or monosomies that usually result in miscarriage. Some chromosome inversions are benign and do not impact prognosis for patients with recurrent pregnancy loss. However, others may have significant reproductive phenotypes. All patients with balanced chromosome rearrangements should undergo genetic counseling prior to attempting conception to better understand their individual risks. Neither family history alone nor a history of prior term births is sufficient to rule out a potential parental chromosomal abnormality. Whereas the frequency of detecting a parental chromosomal abnormality is inversely related to the number of previous spontaneous losses, the chance of detecting a parental chromosomal abnormality is increased among couples who have never experienced a live birth (13). Testing for parental karyotopes in couples with recurrent miscarriage is recommended but some argue it has a high cost for discovery of a rare cause for recurrent pregnancy loss with limited treatment options. Proponents of testing indicate it promotes benefits that include permitting patient autonomy in choosing options for treatment and identification of patients at risk for offspring with unbalanced translocations who may have birth defects.
A couple with a balanced translocation has a high chance of live birth attempting to conceive via intercourse (339); or they have the option of screening embryos for chromosome arrangements with in vitro fertilization (IVF) (338). Studies to date evaluating the use of IVF with chromosomal screening for couples with recurrent pregnancy loss and translocations do not show a significantly higher chance of success compared to natural conception (235,340). These studies are limited in patient number and use older technology and techniques like fluorescent in situ hybridization (FISH) and single cell day 3 embryo biopsy (235,340). With advancements such as blastocyst biopsy, alternate chromosome analysis techniques and others, future studies may show a benefit for use of IVF in this population. Based on the existing data, IVF with embryo screening is not strongly recommended for a couple with a balanced translocation and recurrent miscarriage.
Thrombophilias
After combining a known association between the presence of antiphospholipid antibodies, placental dysfunction, and miscarriage with evidence showing subsequent increase in live birth with anticoagulation medications in these patients with recurrent miscarriage (299), attention was turned to investigating inherited thrombophilias as a cause for recurrent pregnancy loss. The clotting cascade is a delicate balance of prothrombotic (see Fig. 33-1) and antithrombotic pathways (see Fig. 33-2) and dysregulation in either or both of these pathways can cause significant health consequences. Because alterations in coagulation occur naturally in pregnancy with relative maternal hypercoagulability secondary to increases in several procoagulant activities, decreases in select antithrombotic pathways and venous stasis, the delicate balance between pro- and antithrombotic would seem to be even more tenuous throughout gestation (see Fig. 33-3). [5]
Despite the biologic plausibility that patients with recurrent miscarriage would have a higher prevalence of inherited thrombophilia and that anticoagulation of patients with these diagnoses would decrease risk of subsequent miscarriage, the evidence does not support the theories (341).
Table 33-1 Proposed Etiologies and Testing for Recurrent Spontaneous Miscarriage
FIGURE 33-1 The clotting cascade. Physiologic clotting is initiated by endothelial cell damage or abnormal exposure of negatively charged phospholipids to serum and blood components. Procoagulant pathways in black are part of the clotting cascade and are prothrombotic. Both lead to activation of cascades of proteolytic enzymes and cleavage of clotting factors. The extrinsic and intrinsic pathways are initiated by distinct mechanisms. They merge at the activation of factor X to form the common pathway. For all coagulation factors, the subscript letter “a” denotes the activated form of the factor.
FIGURE 33-2 Physiologic mechanisms that counteract the clotting cascade. The procoagulant cascade is inhibited by several physiologic mechanisms. The balance between pro- and antithrombotic pathways determines the state of coagulability.
Antithrombotic mechanisms include the action of antithrombin (AT) and of proteins C and S. The sites of inhibition by these substances are depicted by an “X.” Plasminogen activator inhibitors-1 and -2 (PAI-1 and PAI-2) indirectly inactivate plasmin. Plasmin plays an important role in the dissolution of coagulated blood. For all coagulation factors, the subscript letter “a” denotes the activated form of the factor. FSP, fibrin split products; FDP, fibrin degradation products.
FIGURE 33-3 Alterations coagulation and fibrinolysis during normal pregnancy.
Pregnancy is a state of hypercoagulability. Levels of factors VII, VIII, X, and XII are elevated throughout pregnancy, levels of factors II, V, and XIII rise in the first trimester, then return to normal values. The antithrombotic activity mediated by protein S decreases in pregnancy. The placenta produces plasminogen activator inhibitor-2 (PAI-2). For all coagulation factors, the subscript letter “a” denotes the activated form of the factor. FSP, fibrin split products; FDP, fibrin degradation products.
Inherited thrombophilia is a genetic predisposition to venous thromboembolism and traditionally includes factor V Leiden (FVL) mutation, prothrombin gene mutation, protein C deficiency, protein S deficiency, and antithrombin III deficiency. It is estimated that up to 15% of the Caucasian population carries an inherited thrombophilic mutation (15). FVL is a clotting protein that works in conjunction with activated factor X to convert prothrombin to thrombin. One comprehensive review shows that carriers for FVL have an increased relative risk of recurrent pregnancy loss (342), however, the absolute risk of miscarriage in this population is low (343).
Prothrombin gene mutation results in a deficiency of thrombin and resulting increased concentration of prothrombin in the plasma. Some small studies have shown a potential association between a mutation in the prothrombin gene and recurrent pregnancy loss but overall recommendations do not support an association with this mutation and any pregnancy complication including miscarriage, intrauterine growth restriction, or preeclampsia (342,343). Protein S and Protein C in combination are required for factor V and VIII activation and thus deficiency in either can lead to a hypercoagulable state. Patients with protein S or protein C deficiencies may be at slightly higher risk of thrombosis in pregnancy but associations with miscarriage risk have not been definitively demonstrated (344). Antithrombin is a small protein that regulates clot formation by inactivating factor Xa and thrombin. Deficiency in this protein leads to high risk of thrombosis and increased risk of miscarriage (344). Because of its low prevalence (1/2,500), antithrombin deficiency is not recommended for routine screening for recurrent miscarriage in the absence of significant family history of thrombosis (345).
Although not usually considered an inherited thrombophilia, a methylenetetrahydrofolate reductase (MTHFR) mutation may be associated with increased thrombosis risk and some suggest an association with recurrent pregnancy loss. MTHFR is an essential enzyme for folic acid metabolism and is responsible for converting homocysteine to methionine. A mutation in the enzyme may cause increased serum levels of homocysteine that may lead to a hypercoagulable state (see Fig. 33-4). There are two predominant mutations (C677T and A1298C) and they are common in certain populations with up to 40% of Caucasian and Hispanic populations being heterozygote for the C677T mutation (346). Some suggest that a mutation leads to lower function of the MTHFR enzyme resulting in higher homocysteine levels and increased risk of thrombosis and miscarriage but the association is controversial (347).
FIGURE 33-4 Homocysteine metabolism. Dietary methionine is metabolized either to cysteine or back into methionine. Homocysteine, a prothrombotic metabolite, is an
intermediate in this process. Conversion of homocysteine to methionine requires transfer of
a methyl group from 5-methyltetrahydrofolate. The conversion of folate to 5-
methyltetrahydrofolate is a multistep process requiring vitamin B2 as a cofactor for the
enzyme, methylene tetrahydrofolate reductase (MTHFR). Vitamin B12 is a required
cofactor for the enzyme methionine synthase. Vitamin B6 is also required for metabolism
of sulfur-containing amino acids such as methionine.
The proposed mechanistic basis for the association between adverse fetal
outcomes and heritable thrombophilias has focused on impaired placental
development and function, secondary to venous and/or arterial thrombosis at
the maternal–fetal interface. These findings have been noted in the placentas of
women with adverse fetal outcomes and known inherited thrombophilias and
have been demonstrated in patients with similar outcomes, but lacking inherited
thrombophilic risk (18–22). Detractors of placental thrombosis as causal in early
pregnancy losses (<10 weeks’ gestation) cite an elegant series of experiments
demonstrating that maternal blood flow into the intervillous spaces of the human
placenta does not occur until approximately 10 weeks of gestation (23–26). Prior
to the establishment of intervillous circulation, nutrient transfer from maternal
1972blood to fetal tissues appears to be dependent on transudation that, in turn, relies
on flow through the uterine vasculature. This suggests that maternal or fetal
thrombotic episodes in the developing placental vasculature could be equally
devastating prior to or after the establishment of intervillous circulation near 10
weeks of gestation. Very early pregnancy losses (biochemical, anembryonic) and
known aneuploid fetal losses are unlikely to be altered by the presence of, or
treatment for, an underlying thrombophilic state.
[5] Neither the American College of Obstetrician Gynecologists (ACOG) nor the American Society of Reproductive Medicine (ASRM) recommend screening for inherited thrombophilias or MTHFR mutations for patients with recurrent pregnancy loss or any adverse pregnancy outcome (338,345) unless other risk factors are present, such as a history of thrombosis in the patient or a close family member. Despite the lack of evidence and guidelines against routine screening for thrombophilia in recurrent pregnancy loss, many clinicians routinely order these tests (347,348).
Anatomic Abnormalities
Anatomic abnormalities of both the uterine cervix and the uterine body have been associated with recurrent pregnancy loss (28,29). These anatomic causes may be either congenital or acquired. During development, the uterus forms via the
apposition of a portion of bilateral hollow tubes called the müllerian ducts. The
dissolution of the walls of these ducts along their site of apposition allows
formation of the intrauterine cavity, the intracervical canal, and the upper vagina.
Congenital uterine anomalies may therefore include incomplete müllerian duct
fusion, incomplete septum resorption, and uterine cervical anomalies. Although
the causes underlying many of the congenital anomalies of the female
reproductive tract are unclear, it has been well-documented that prenatal exposure
to maternally ingested diethylstilbestrol (DES) results in complex congenital
uterine, cervical, and vaginal changes.
Historically, all congenital reproductive tract abnormalities have been linked to
isolated spontaneous pregnancy loss and recurrent pregnancy loss, although the
presence of an intrauterine septum and prenatal exposure to DES demonstrate the
strongest associations (30–32). Women with an intrauterine septum may have as
high as a 60% risk for spontaneous miscarriage (33). Uterine septum–related
losses most frequently occur during the second trimester (34). If an embryo
implants into the poorly developed endometrium overlying the uterine septum,
abnormal placentation and resultant first trimester losses may occur (35). The
most common uterine congenital anomaly associated with in utero DES exposure
is hypoplasia, which may contribute to first- or second-trimester pregnancy
losses, incompetent cervix, and premature labor (36,37). Congenital anomalies of
1973the uterine arteries may contribute to pregnancy loss via adverse alterations in
blood flow to the implanted blastocyst and developing placenta (38).
Acquired anatomic anomalies have likewise been linked to isolated and
recurrent pregnancy losses. These abnormalities include such disparate conditions
as intrauterine adhesions, uterine fibroids, and endometrial polyps. Endometrium
that develops over an intrauterine synechiae or over a fibroid that impinges in the
intrauterine cavity (submucous) may be inadequately vascularized (39). This may
promote abnormal placentation for any embryo attempting to implant over such
lesions. Although data supporting these concepts are limited, this abnormal
placentation may lead to spontaneous pregnancy loss. Less clear is the association
between intramural fibroids and recurrent pregnancy loss, but it is suggested that
large (≥5 cm) intramural fibroids are associated with pregnancy loss and that
removal improves outcomes (see Chapter 11) (32,40).
Endocrine Abnormalities
The endocrinology of normal pregnancy is complex. Because spontaneous
pregnancy is critically dependent on appropriately timed endocrinologic
changes of the menstrual cycle, it is not surprising that those endocrine
abnormalities that alter pregnancy maintenance may have their effects
during the follicular phase of the cycle in which conception occurs, or even
earlier. Modifications in follicular development and ovulation, in turn, may be
reflected in abnormalities of blastocyst transport and development, alterations in
uterine receptivity to the implanting blastocyst, and improper functioning of the
corpus luteum. Endocrinologic factors suggested to be associated with recurrent
miscarriage include luteal phase insufficiency, hypersecretion of luteinizing
hormone (LH), thyroid disease, and, potentially, insulin resistance and polycystic
ovarian syndrome (PCOS), diabetes mellitus, hyperprolactinemia, and decreased
ovarian reserve.
Beginning with ovulation and lasting until approximately 7 to 9 weeks of
gestation, maintenance of early pregnancy depends on the production of
progesterone by the corpus luteum. Normal pregnancies are characterized by a
luteal–placental shift at about 7 to 9 weeks of gestation, during which the
developing placental trophoblast cells take over progesterone production and
pregnancy maintenance (41). Spontaneous pregnancy losses occurring before 10
weeks of gestation may result from a number of alterations in normal
progesterone production or utilization. These include failure of the corpus luteum
to produce sufficient quantities of progesterone, impaired delivery of
progesterone to the uterus, or inappropriate utilization of progesterone by the
uterine decidua. Pregnancy failures may occur near the time of the expected
luteal–placental shift if the trophoblast is unable to produce biologically active
1974progesterone following demise of the corpus luteum.
Luteal phase insufficiency or luteal phase defects are characterized by
inadequate luteal milestones and most likely relate to adverse pregnancy outcome
via inadequate or improperly timed endometrial development at potential
implantation sites. An elegant description of abnormalities at the site of
implantation, which may be responsible for some cases of recurrent pregnancy
loss, describes impaired decidualization of the endometrium as a mechanism for
natural selection of human embryos (42). Luteal phase defect has many causes,
some of which are associated with hypersecretion of LH. Although the
mechanism underlying the association of elevated LH levels with recurrent
pregnancy loss is incompletely understood, abnormal LH secretion may have
direct effects on the developing oocyte (premature aging), on the endometrium
(dyssynchronous maturation), or both. Many patients with elevated LH levels also
display physical, endocrinologic, and metabolic characteristics of PCOS.
Some studies report ovarian radiologic evidence of PCOS in as many as 40% to
80% of recurrent pregnancy loss patients (43,44). In addition to inappropriately
elevated LH levels, PCOS patients are frequently obese and often have elevated
circulating androgen levels. Although controversial, both changes have been
linked to recurrent pregnancy loss, and elevated androgen levels have been shown
to adversely affect markers of uterine receptivity in women with a history of
recurrent pregnancy loss (43–46). Many women with PCOS have metabolic
alterations in glycemic control characterized by insulin resistance. This too may
be directly or indirectly related to adverse pregnancy outcome, and it may explain
increases in the rate of spontaneous pregnancy loss among women with type 2
diabetes mellitus (47). Women with overt insulin-dependent diabetes mellitus
(IDDM) appear to exhibit a threshold of pregestational glycemic control above
which spontaneous pregnancy loss is increased (48,49). Hyperglycemia has been
directly linked to embryonic damage (50). In cases of advanced IDDM with
accompanying vascular complications, compromised blood flow to the uterus
may be mechanistically involved in subsequent pregnancy loss.
Patients with thyroid disease often have concomitant reproductive
abnormalities, including ovulatory dysfunction and luteal phase defects. The
metabolic demands of early pregnancy mandate an increased requirement for
thyroid hormones. It is therefore not surprising that hypothyroidism has been
associated with isolated spontaneous pregnancy loss and with recurrent pregnancy
loss (51). The definition of hypothyroidism is itself now under scrutiny with
many investigators suggesting that cutoff thyroid-stimulating hormone (TSH)
values during pregnancy should be less than 2.5 mIU/mL (52). Others have
suggested even lower TSH cutoff values (53). Although it has long been debated
whether clinically euthyroid patients with antithyroid antibodies have higher rates
1975of miscarriage and recurrent pregnancy loss, thyroid hormone supplementation
was shown to reduce miscarriage in infertility patients with positive antithyroid
antibodies and otherwise normal TSH levels undergoing IVF (54–60). The
mechanism for an association between antithyroid antibody positivity and
recurrent pregnancy loss remains unclear; however, these antibodies could be
markers of more generalized autoimmunity or may predict an impaired ability of
the thyroid gland to respond to the demands of pregnancy.
Elevated prolactin levels have been associated with miscarriage and recurrent
miscarriage. Hyperprolactinemia has been associated with ovulatory dysfunction
and may result in miscarriage via alterations in the hypothalamic–pituitary–
ovarian axis resulting in impaired folliculogenesis, oocyte maturation or luteal
phase dysfunction (61–63). One study in patients with hyperprolactinemia and
recurrent pregnancy loss showed a higher live birth rate in a subsequent
pregnancy after normalization of prolactin levels with a dopamine agonist (63).
Some studies have shown an association between diminished ovarian reserve
(DOR) and recurrent miscarriage (64,65). Shahine et al. suggests that this link
may result from an association between DOR and increased risk of aneuploid
embryos (349). Aneuploidy (chromosomal aberrations) is the most common cause
of first trimester miscarriage and women with DOR have a higher percentage of
aneuploid embryos compared to age-matched controls in both the recurrent
pregnancy loss (349) and the nonrecurrent pregnancy loss patient populations
(350). Ovarian reserve testing (early follicular phase follicle stimulating hormone
level, estradiol, and anti-müllerian hormone levels) is not currently recommended
by ASRM for the evaluation of recurrent miscarriage. DOR can explain higher
risk of miscarriage caused by higher risk of aneuploidy and help guide patients
regarding the next steps in care. Increasingly, IVF with chromosomal screening of
embryos is offered as a treatment option for women with recurrent pregnancy loss
(351) but success is minimal in the setting of DOR and may not be higher than
success without intervention (352).
Maternal Infection
The association of infection with recurrent miscarriage is among the most
controversial and poorly explored of the potential causes for pregnancy loss.
Reproductive tract infection with bacterial, viral, parasitic, zoonotic, and
fungal organisms have all been theoretically linked to pregnancy loss;
however, mycoplasma, ureaplasma, chlamydia, and a-streptococcus are the
most commonly studied pathogens (66,67). There is data that directly addressed
the roles of some of these proposed organisms in recurrent pregnancy loss. One
prospective comparison trial involving 70 recurrent pregnancy loss patients
reported no elevations in any markers for present or past infection with
1976Chlamydia trachomatis when compared with controls (68). In contrast, a very
large, prospective trial demonstrated a link between the detection of bacterial
vaginosis and a history of second trimester pregnancy loss among 500 recurrent
pregnancy loss patients (69). The risk of bacterial vaginosis detection was
positively correlated with cigarette smoking in this study.
The etiologic mechanism linking specific organisms to either isolated or
recurrent pregnancy loss remains unclear and must certainly differ among
infectious organisms. Certain viral organisms, such as herpes simplex virus
(HSV) and human cytomegalovirus (HCMV), can directly infect the placenta
and fetus (70,71). The resulting villitis and related tissue destruction may lead to
pregnancy disruption. Another theoretic possibility warranting study is that
infection-associated–early pregnancy loss may result from immunologic
activation in response to pathologic organisms. A large body of evidence supports
the role of this mechanism in adverse events later in gestation, such as intrauterine
growth restriction, premature rupture of membranes, and preterm birth (72,73).
Alternatively, mechanisms that protect the fetus from autoimmune rejection may
protect virally infected placental cells from recognition and clearance. This could
potentially promote periods of unfettered infectious growth for some of the
pathogenic organisms gaining entry to the reproductive tract (74).
Chronic endometritis, defined as the asymptomatic presence of histologically
documented plasma cells in an endometrial biopsy, may be associated with
recurrent miscarriage. Studies have shown a prevalence of 7% to 13% based on
morphologic assessment alone (353,354) and up to 56% in patients with recurrent
pregnancy loss (354). Chronic endometritis is associated with previous infections
and retained pregnancy tissue and, despite the difficulty of determining cause and
effect, treatment with antibiotics shows a higher live birth rate in subsequent
pregnancies in some studies (353,354). Endometrial biopsy for chronic
endometritis diagnosis and treatment are not recommended by expert groups and
larger studies are needed before implementing evaluation and treatment in routine
practice.
Immunologic Phenomena
[5] Embryo implantation and pregnancy maintenance is a delicate interaction and
balance between maternal and embryonic/fetal immune, hormonal, and
coagulation systems. Maternal rejection of paternal antigens and immune system
dysfunction as a cause of recurrent miscarriage has been explored extensively but
remains controversial (75). Laboratory testing for immune dysfunction can be
misleading and the treatments aimed at maternal immunosuppression can have
significant side effects. Expert groups have omitted immune testing and
recommended against extensive immunosuppression as a treatment for
1977unexplained recurrent miscarriage (338).
A brief review of some of the important concepts in basic immunology is
warranted to place testing and treatment discussions in context. Immune
responses classically are divided into innate and acquired responses. Innate
responses represent the body’s first line of defense against pathogenic
invasion. They are rapid and are not antigen specific. Cell types and mechanisms
typically considered vital to innate immunity include complement activation,
phagocytosis by macrophage, and lysis by natural killer (NK) and natural killer T
(NKT) cells and possibly by TCR γ δ+ T cells. Acquired immune responses, in
contrast, are antigen specific and are largely mediated by T cells and B cells.
Acquired responses can be further divided into primary (response associated
with initial antigen contact) and secondary (rapid and powerful amnestic
responses associated with subsequent contact to the same antigen).
Antigen specificity is regulated by two sets of genes in the major
histocompatibility complex (MHC), located on chromosome 6 in humans. MHC
class I molecules (human leukocyte antigen [HLA]-A, -B, and -C) are present
on the surface of nearly every cell in the human body and are important in
defense against intracellular pathogens, such as viral infection and oncogenic
transformation. MHC class I molecules act as important ligands for both the Tcell receptor on CD8+ cytotoxic/suppressor T cells and for a variety of receptors
on NK cells (76). MHC class II molecules (HLA-DR, HLA-DP, and HLADQ), in contrast, are present on the surface of a limited number of antigenpresenting cells, including dendritic cells, macrophage and monocytes, B
cells, and tissue-specific cells such as the Langerhans cells in the skin. These
molecules are important in defense against extracellular pathogens, such as
bacterial invaders. The major ligand for MHC class II is the T-cell receptor on
CD4+ T helper cells.
One very important concept in immunology that has particular
application to pregnancy is that of immune tolerance. The passage of bone
marrow–derived T cells through the fetal thymus during early development has
been well described. In this developmental interval, the T cells encounter a
process termed thymic education. During thymic education, T cells that express
either the CD4 or the CD8 coreceptor are chosen, and autoreactive cells are
effectively eliminated. This education promotes T-cell tolerance, allowing
selection and survival exclusively of those T cells that recognize nonself and will
not react against self (80,81).
Cellular Immune Mechanisms
Three main questions summarize much of the theoretical thinking surrounding
pregnancy maintenance and reproductive immunology:
19781. Which immune cells populate the reproductive tract, particularly at
implantation sites?
2. How do the characteristics of antigen presentation differ at the maternal–fetal
interface?
3. What regulatory mechanisms specifically affect reproductive tract immune
cells?
Resident Cells: Natural Killer Cells and T Regulatory Cells
Immune cells populating the reproductive tract exhibit many characteristics
that distinguish them from their peripheral counterparts. In particular, the
human endometrium is populated by T cells, macrophage, and NK-like cells,
but very few B cells are present. The relative proportions of these resident cells
vary with the menstrual cycle and change dramatically during early pregnancy.
Surrounding the time of implantation, one particular cell type comprises between
70% and 80% of the total endometrial lymphocyte populations (82,83). This cell
type is called a variety of names, including decidual granular lymphocytes
(DGLs), large granular lymphocytes (LGLs), and decidual NK cells. This
heterogeneity of names reflects the fact that this particular cell type differs from
similar cells isolated from the periphery, although most believe it to be an NK cell
variant. While most peripheral NK cells have low cell surface expression of CD56
(CD56dim) and express high levels of CD16, the immunoglobulin receptor
responsible for NK-mediated, antibody-dependent cellular cytotoxicity, those in
the uterine decidua and at the placental implantation site, are largely CD56bright
and CD16dim or CD16− (84). If these unusual endometrial cells are considered
NK cells, the implantation site represents the largest accumulation of NK cells in
any state of human health or disease. These decidual NK cells display fairly poor
cytotoxic function but are robust cytokine secretors (85,86). The balance of
activating and inhibitory receptors expressed on their cell surfaces determines
their ultimate killing versus secretion patterns (87,88).
The role of NK cells in reproduction and recurrent pregnancy loss is
controversial. Some studies show increased levels of CD56 NK cells (those with
killer-type activating receptors) in peripheral blood of women with recurrent
pregnancy loss compared to controls (89,90) and other studies do not show a
difference (355,356). The studies showing a difference may be inherently flawed.
Most of the recurrent miscarriage patients included in the study were nulliparous
and the controls were multiparous (357); a previous successful pregnancy can
induce permanent changes in NK subsets (358). Some studies have shown that a
higher level of NK cytotoxicity in the peripheral blood before pregnancy resulted
in a higher rate of pregnancy loss (359), while other studies showed similar NK
1979cytotoxicity in recurrent pregnancy loss patients with subsequent pregnancy loss
or live birth (360). Results from studies of NK cell levels in endometrial tissues in
recurrent miscarriage vary; some showing higher levels of CD56 NK cells in the
endometrial tissue from recurrent pregnancy loss patients (94) and others showing
lower levels (95). Interpretation of NK cell levels in endometrial tissue can be
limited by the inherent variability of levels throughout the different menstrual
cycle stages and the questionable testing accuracy using either immunochemistry
or flow cytometry (361). A strong argument against using any NK cell testing in
the evaluation of recurrent miscarriage patients comes from a large prospective
study showing that high NK toxicity before pregnancy did not impact subsequent
pregnancy loss rate (362).
A subpopulation of CD4+ T cells has been described that, like all activated
lymphocytes, strongly expresses CD25 on their cell surface (77). These CD4+
CD25+ cells are more specifically identified by the intracellular presence of the
forkhead box P3 (Fox P3) transcription factor and have been called regulatory T
lymphocytes (Treg cells). Treg cells, when activated by autoantigens, can
suppress activated inflammatory cells. They secrete regulatory cytokines,
including interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) (77–
79). They may impact avoidance of tissue destruction associated with
inflammation and may play a central role in pregnancy maintenance. In pregnant
mice and women, these specialized CD4+ cells are systemically expanded in an
alloantigen independent fashion and can suppress adverse maternal responses to
the fetus (92) and to self (93).
The human decidua contains characteristic immune effector cells. These
immune cell populations are reported to be altered in recurrent pregnancy loss
patients but not in patients experiencing isolated spontaneous pregnancy losses
(91,94–96). Most investigations into whether alterations in these cells (including
T cells, decidual NK cells, and NKT cells) determine pregnancy outcome are
hampered by insufficient patient numbers to allow meaningful conclusions. [5]
Further research is needed to understand the role of NK cells and T regulatory
cells in reproduction and miscarriage. Expert groups do not recommend testing
recurrent pregnancy loss patients for NK cell cytotoxicity or Treg cells and any
treatment targeted toward suppression of these immune cells should be conducted
only in the setting of a clinical trial.
Antigen Presentation at the Maternal–Fetal Interface
Historically, it was proposed that the implanting trophoblastic allograft could
make itself antigenically invisible to avoid immune detection by the maternal
host. It could downregulate its expression of the MHC-encoded transplantation
antigens (some of which would be of paternal origin) and thereby avoid
1980recognition as nonself. Although immunology studies rendered this theory
obsolete, the implanting fetus does utilize this strategy to the extent (97) that
placental trophoblast cells do not express MHC class II molecules (98,99). Unlike
nearly every other cell in the human body, trophoblast cells do not express
the classical MHC class I transplantation antigens HLA-A and -B. Rather, a
subpopulation of placental cells, specifically the extravillous cytotrophoblast
cells, express the classical MHC class I HLA-C products, and the nonclassical
HLA-E, -F, and -G products (74,100–104). These extravillous cytotrophoblast
cells are of particular interest because they are characterized by remarkable
invasive potential (105,106). These cells move from the tips of the anchoring
villae of the human placenta, invading deeply into the maternal decidua, and some
replace cells within the walls of decidual arterial vessels (105–107). Although the
invasive characteristics of extravillous cytotrophoblast may reflect non-MHC–
related mechanisms, including well-described integrin switching, the intimate
contact of these fetal-derived cells with maternal immune effector cells exposes
the fetus to recognition as nonself (108) and it is now apparent that the pregnant
woman recognizes and responds to paternally-derived antigens. These responses
appear to be essential to pregnancy maintenance but must be tightly regulated.
It is not known why all placental cells downregulate expression of HLA-A and
-B, whereas invasive extravillous cytotrophoblast express HLA-C, -E, and -G.
This area of investigation is ripe with hypotheses and study. Because NK cells of
the innate immune system recognize and kill cells that express no MHC, the
complete downregulation of MHC should cause trophoblast cells to act as targets
for those NK cells that are pervasive at sites of implantation (88,97). In addition
to possible protection from direct NK cell–mediated killing, the expression of
HLA-C, -E, and -G by trophoblast cells may serve a variety of alternate purposes.
NK cell receptor–mediated interactions with extravillous cytotrophoblast MHC
products modulate cytokine expression profiles at the maternal–fetal interface
(85,86). MHC expression aids in decidual and vascular invasion by the
trophoblast, an activity essential for proper placental development (109).
Whereas definitive correlations between placental MHC class I expression
patterns and recurrent pregnancy loss remain contentious, trophoblast expression
of HLA-G was linked to other disorders of placental invasion, such as
preeclampsia (109,110). Genetic mutations at the HLA-G locus have been linked
to recurrent pregnancy loss in some, but not all studies (111–114). Soluble or
secreted trophoblast MHC products may aid in the development of maternal
immune tolerance toward the placenta (115). Soluble HLA-G has been shown to
suppress T lymphocyte and NK cell function and to induce the expansion of Treg
cells in humans (116).
Aberrant expression of class II MHC determinants, or enhanced expression of
1981MHC class I on syncytiotrophoblast in response to IFN-γ (117) could mediate
pregnancy loss by enhancing cytotoxic T cell attack (118). This theory appears
unlikely, because the expression of classical MHC antigens does not seem to be
induced on aborted tissues from women experiencing one or more pregnancy
losses (118). MHC class II genotypes appear to affect susceptibility to a variety of
diseases, including diabetes and other autoimmune diseases. A similar link
between MHC class II typing and adverse pregnancy outcome was reported
for recurrent pregnancy loss (119,120).
Regulation of Decidual Immune Cells
The characteristics of the interactions between decidual immune effector cells and
the implanting fetus may be determined by factors other than those already
mentioned. As might be predicted, these regulatory effects are often targets for
investigative efforts, because they may offer more direct insight into potential
therapies for immune-mediated disorders of pregnancy maintenance. Three such
regulatory mechanisms will be discussed here: (a) alterations in T helper cell
phenotypes; (b) reproductive hormones and immunosuppression; and (c)
tryptophan metabolism.
Antigen-stimulated immune responses involving CD4± T cells can be divided
into two major classes: T helper 1 (TH1) responses and T helper 2 (TH2)
responses. This subclassification is overly simplified, but it has been useful in
broadly defining types of immune responses based on the characteristics of the
CD4± cells present, and their associated cytokines. Cytokines are signaling
molecules secreted from immune cells that bind to receptors on other immune
cells to either stimulate or inhibit function. TH1 and TH2 immune cells express
different cytokines with different functions and studies suggest that successful
embryo implantation ultimately occurs in a TH2 dominant environment and that
poor pregnancy outcomes may result if the balance favors a TH1 dominant
environment (363). Studies have suggested that TH1-type cytokines can be
harmful to implanting developing embryo (121,122) and that some patients with
recurrent pregnancy loss exhibit a local dysregulation of their T helper cellular
immune response to antigens, with typical shifts toward TH1 inflammatory
responses at the maternal–fetal interface (123,124). This remains difficult to study
and prove given that the dominant immune cell population (TH1 or TH2) is
usually determined by peripheral blood levels of cytokines and cytokines display
their results at close range. Measurements of cytokines in peripheral blood,
endometrial biopsies, or flushing of decidual tissue are subject to technical
difficulties and conclusions about cytokines and their role in recurrent pregnancy
loss are yet to be determined. TNF-α is one cytokine that can usually be detected
easily in the blood with most assays and may be a good marker for inflammation.
1982Studies have shown higher levels of TNF-α in women with recurrent pregnancy
loss in early pregnancy (364).
Although many mechanisms are aimed at avoiding maternal immune
recognition of the implanting fetus, research in humans and animals
indicates that immune responses to fetal antigens are present (126–128).
Thus, the regulation of this response at the maternal–fetal interface may be
critical. Reproductive hormones have dramatic effects on peripheral cell–
mediated immunity, as demonstrated by well-documented and notable gender
differences in immune responsiveness (129). The levels of these potentially
immunosuppressive hormones are quite elevated in the circulation of pregnant
women. The fact that the levels of these hormones at the maternal–fetal interface
may be dramatically higher than those in the maternal circulation during
pregnancy may help to explain an apparent inconsistency: with some exceptions,
overall immune responsiveness during pregnancy appears to change a little, while
local modulation at the maternal–fetal interface may be vital (130).
It has been suggested that the immunosuppressive effects of progesterone
within the reproductive tract are at least partially responsible for the maintenance
of the semiallogeneic implanting fetus (131). In vitro studies have shown that
progesterone mediates its suppression of T cell effector function by altering
membrane-resident potassium channels and cell membrane depolarization. This
action, in turn, affects intracellular calcium signaling cascades and gene
expression and may be mediated by nonclassical steroid receptors or may not
involve a receptor at all (132–134). Progesterone-mediated changes in T cell gene
expression have been associated with the development of TH2-type T helper cell
responses and with increased leukemia inhibitory factor (LIF) expression (135).
Because a shift in the intrauterine immune environment from TH2 to TH1 has
been linked with early spontaneous pregnancy loss, the elevated intrauterine
concentrations of progesterone characteristic of early pregnancy may promote an
immune environment favoring pregnancy maintenance (123). To this point, in
vitro evidence indicates that progesterone can inhibit mitogen-induced
proliferation of and cytokine secretion by CD8+ T cells and can alter the
expression of a transcription factor that drives the development of TH1 cells
(136,137).
Levels of estrogen rise markedly during pregnancy, and attention has focused
on the role of estrogen in immune modulation. A group of animal studies showed
that estrogens improve immune responses in males after significant trauma and
hemorrhage, suppress cell-mediated immunity after thermal injury, and protect
against chronic renal allograft rejection (138–140). In vitro, estrogens appear to
downregulate delayed-type hypersensitivity (DTH) reactions and promote the
development of TH2-type immune responses, particularly at the elevated estrogen
1983concentrations typical of pregnancy (141,142). In mice, elevations in estrogen
have been shown to recruit Treg cells to the uterus (390).
One additional regulatory mechanism proposed for the induction of maternal
tolerance to the fetal allograft involves the amino acid tryptophan and its
catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). The IDO hypothesis of
tolerance in pregnancy rests on data showing that T cells need tryptophan for
activation and proliferation (143) and local alterations in tryptophan metabolism
at the maternal–fetal interface could either activate or fail to suppress maternal–
antifetal immunoreactivity (144). Studies in mice have shown that the inhibition
of IDO leads to loss of allogeneic, but not syngeneic, fetuses, and that this effect
is mediated by lymphocytes (145). Further support lies in studies demonstrating
that hamsters fed diets high in tryptophan have increased rates of fetal wastage
(146). Extending this theory to humans requires further investigation. However,
the demonstration of IDO expression in human uterine decidua, and the
documentation of alterations in serum tryptophan levels with increasing
gestational age during human pregnancy support further interest in this potential
local immunoregulatory mechanism (147,148).
Humoral Immune Mechanisms and Antiphospholipid Syndrome
Humoral responses to pregnancy-specific antigens exist, and patients with
recurrent pregnancy loss can display altered humoral responses to
endometrial and trophoblast antigens (123,149). Nevertheless, most literature
surrounding humoral immune responses and recurrent pregnancy loss focus on
organ nonspecific autoantibodies associated with the antiphospholipid syndrome
(APS). Historically, these immunoglobulin-G (IgG) and IgM antibodies were
considered to be directed against negatively charged phospholipids. Those
phospholipids most often implicated in recurrent pregnancy loss are cardiolipin
and phosphatidylserine. However, antiphospholipid antibodies often are directed
against a protein cofactor, β2 glycoprotein 1, which assists antibody association
with phospholipid (150–154). Antiphospholipid antibodies were originally
characterized solely by prolonged phospholipid-dependent coagulation tests in
vitro (activated partial thromboplastin time [aPTT], Russell viper venom time)
and by thrombosis in vivo. The association of these antiphospholipid antibodies
with thrombotic complications has been termed the APS, and although many of
these complications are systemic, some are pregnancy specific—spontaneous
miscarriage, stillbirth, intrauterine growth retardation, and preeclampsia
(155,156). A reassessment of the criteria used to diagnose APS resulted in
additions to the prior Sapporo criteria for diagnosis of APS and continues to
include adverse pregnancy outcomes. These criteria, which have been validated
clinically, are as follows (156–158):
1984For a patient to be diagnosed with antiphospholipid syndrome, one or more
clinical and one or more laboratory criteria must be present:
Clinical
1. One or more confirmed episode of vascular thrombosis of any type:
Venous
Arterial
Small vessel
2. Pregnancy complications:
Three or more consecutive spontaneous pregnancy losses at less than
10 weeks of gestation with exclusion of maternal anatomic and
hormonal abnormalities and exclusion of paternal and maternal
chromosomal abnormalities
One or more unexplained deaths of a morphologically normal fetus at
or beyond 10 weeks of gestation (normal fetal morphology documented
by ultrasound or direct examination of the fetus)
One or more premature births of a morphologically normal neonate at
or before 34 weeks of gestation secondary to severe preeclampsia or
placental insufficiency
Laboratory
Testing must be positive on two or more occasions with evaluations 12 or more
weeks apart:
1. Positive plasma levels of anticardiolipin antibodies of the IgG or IgM isotype
at medium to high levels
2. Positive plasma levels of lupus anticoagulant
3. Anti-β2 glycoprotein-1 antibodies of the IgG or IgM isotype in titers greater
than the 99th percentile
The presence of antiphospholipid antibodies (anticardiolipin or lupus
anticoagulant) and anti-β2 glycoprotein-1 antibodies during pregnancy is a
major risk factor for an adverse pregnancy outcome (150,151,159). In a large
series of couples with recurrent pregnancy loss, the incidence of the APS was
between 3% and 5% (66). The presence of anticardiolipin antibodies among
patients with known systemic lupus erythematosus portends less favorable
pregnancy outcomes (160).
Several mechanisms have been proposed by which antiphospholipid
1985antibodies might mediate pregnancy loss (161). Antibodies against
phospholipids could increase thromboxane and decrease prostacyclin synthesis
within placental vessels. The resultant prothrombotic environment could promote
vascular constriction, platelet adhesion, and placental infarction (162–164).
Alternatively, in vitro evidence from trophoblast cell lines indicates that IgM
action against phosphatidylserine inhibits formation of syncytial trophoblast
(165). Syncytialization is required for proper placental function. One study
demonstrated that both extravillous cytotrophoblast and syncytiotrophoblast cells
synthesize β2 glycoprotein-1, the essential cofactor for antiphospholipid antibody
binding (166). Although it gives insight into pathophysiology, the prognostic
value of serum levels of specific antibodies against β2 glycoprotein-1 with respect
to pregnancy outcome among recurrent pregnancy loss patients is contentious and
may be poorer than that of standard anticardiolipin antibodies (167–169). Some
have proposed that sera from antibody positive recurrent pregnancy loss patients
are particularly adept at inhibiting trophoblast adhesion to endothelial cells in
vitro (170). Others noted rapid development of atherosclerosis in the decidual
spiral arteries of patients who test positive for antiphospholipid antibodies (171).
Still others have demonstrated that levels of the placental antithrombotic molecule
—annexin V—are reduced within the placental villa from those women with
recurrent pregnancy loss who are antiphospholipid antibody positive (172).
However, placental pathologic evidence that supports causal involvement of the
antiphospholipid syndrome in pregnancy loss is equivocal. The characteristic
lesions for this syndrome (placental infarction, abruption, and hemorrhage) are
typically missing in women with antiphospholipid antibodies, and these same
pathologic lesions can be found in placentae from women with recurrent
miscarriages who do not have biochemical evidence of antiphospholipid
antibodies (161,173–175).
One additional group of autoantibodies that have been linked to recurrent
pregnancy loss is the antithyroid antibodies. Although the data remain somewhat
controversial, several investigators demonstrated an increased prevalence of these
antibodies among women with a history of recurrent pregnancy loss, even in the
absence of thyroid endocrinologic abnormalities (52,56,57,176–178).
Other antibody-mediated mechanisms for recurrent pregnancy loss have
been proposed, including antisperm and antitrophoblast antibodies, and
blocking antibody deficiency but none have withstood the test of time.
It is important to suggest during this in-depth discussion of the immunemediated mechanisms of isolated and recurrent pregnancy loss that pregnancy
may not require an intact maternal immune system. Supporting this concept are
data showing that agammaglobulinemic animals and women can successfully
reproduce (180). Further, viable births occur among women with severe immune
1986deficiencies and in murine models that lack T and B cells (severe combined
immunodeficiency [SCID] mice) and those that display a congenital absence of
their thymus (nude mice).
[5] Despite the knowledge that most first trimester miscarriages are caused by
aneuploidy and that the only immune-related issue recommended for routine
evaluation and treatment for recurrent miscarriage by expert groups is APS,
providers around the world still test and treat for many different immune issues in
couples with recurrent pregnancy loss. Patients and providers feel pressured for
answers and interventions in the setting of unexplained recurrent pregnancy loss
and immune issues play into the woman’s feelings of guilt and worry that there is
something wrong with her that is causing her to reject her pregnancy. Immunerelated dysfunction in relationship to miscarriage and recurrent pregnancy loss
remains up for debate, additional research, and better understanding.
Immunosuppressive treatments can result in harm and until more is understood,
intervention should be limited to investigations in the setting of Institutional
Review Board (IRB)-approved clinical trials.
Male Factors
Most publications that review testing and treatment for recurrent pregnancy loss
couples, including this chapter, recommend only a single test for the male partner
in the couple—a peripheral blood karyotype. The role of the male partner in the
etiology of recurrent pregnancy loss is understudied, but there is a growing body
of literature suggesting that the development and validation of novel testing and
treatment regimens for the male may prove beneficial (181,182). Detailed
peripheral chromosomal testing of men whose partners experienced recurrent
pregnancy loss revealed an increased incidence of Y chromosome microdeletions
when compared to male partners in fertile and infertile couples (183). Small
studies demonstrated that male partners in couples experiencing recurrent
pregnancy loss have an increased incidence of sperm chromosomal aneuploidy,
particularly sex chromosome disomy, when compared to fertile men (184,365–
367). The addition of specialized testing to a standard semen analysis among men
in couples with recurrent loss revealed reductions in sperm functional testing
(hypo-osmotic swelling, acrosome status, nuclear chromatin decondensation) and
increased DNA fragmentation and lipid peroxidation when compared to fertile
men or historical controls (185–187). The latter results suggest that these men
may have abnormal levels of reactive oxygen species in their semen or that their
sperm cells are particularly sensitive to these compounds. Paternal carriage of the
MTHFR C677T mutation and hyperhomocysteinemia were associated with DNA
damage and recurrent pregnancy loss (188). A single, small, uncontrolled
treatment study using antioxidants among male partners in recurrent pregnancy
1987loss couples who had high levels of sperm DNA damage or semen lipid
peroxidation suggested favorable treatment outcomes (186). The only evidencebased recommended test for a male partner in a couple with recurrent pregnancy
loss is a peripheral blood karyotype and the other tests and interventions remain
under investigation. With more focus on male factor in all aspects of
reproduction, more information may surface about the male factor in miscarriage.
Other Factors
It is increasingly evident that the implantation of the blastocyst within the
uterine decidua involves an exquisitely scripted crosstalk between embryo
and mother. Alterations in this dialogue often result in improper implantation
and placental development. For instance, recurrent pregnancy loss has been linked
to a dysregulation in the expression patterns of vascular endothelial growth
factors (VEGFs) in the developing placenta and their requisite receptors within
the maternal decidua (189). Cellular and extracellular matrix adhesion properties
may be involved in this dialogue. The concept of uterine receptivity has been
emboldened by the description of endometrial integrins and the timing of integrin
switching during implantation (190). Others have reported decreased levels of
endometrial mucin secretion and reductions in the endometrial release of soluble
intercellular adhesion molecule I among women with histories of recurrent
pregnancy loss (191,192). Programmed cell death (apoptosis) may play an
essential role in normal placental development. Alterations in two important
apoptotic pathways—Fas-Fas ligand and bcl2—have been linked to recurrent
pregnancy loss and poor pregnancy outcome (75,193).
Environmental Factors
A variety of environmental factors have been linked to sporadic and recurrent
early spontaneous pregnancy loss. These are difficult studies to perform, because,
in humans, they all must be retrospective and all are confounded by alternative or
additional environmental exposures. Nevertheless, the following factors have
been linked to pregnancy loss: exposure to medications (e.g., antiprogestogens,
antineoplastic agents, anti-inflammatory agents, and inhalation anesthetics),
exposure to ionizing radiation, prolonged exposure to organic solvents, and
exposure to environmental toxins, especially phthalates, bisphenol-A, and heavy
metals (194–197). The latter two exposures have been demonstrated to have
endocrine and immune effects that could lead to poor placentation and subsequent
pregnancy loss (198,199). Lathi et al. showed that maternal BPA levels were
directly associated with increased risk of miscarriage (368). Associations between
spontaneous pregnancy loss and exposures to video display terminals, microwave
1988ovens, high-energy electric power lines, and high altitudes (e.g., flight attendants)
are not substantiated (200,201). There is no compelling evidence that moderate
exercise during pregnancy is associated with spontaneous miscarriage.
Association between stress and miscarriage risk is controversial (369). In the
absence of cervical anatomic abnormalities or incompetent cervix, coitus does not
appear to increase the risk for spontaneous pregnancy loss (202,203).
Exposure to four particular substances—alcohol, cigarettes, marijuana, and
caffeine—deserves specific attention; all have been linked with increased risk of
miscarriage through studies with widely varied findings. Although some
conflicting data exist, one very large epidemiologic study has shown that alcohol
consumption during the first trimester of pregnancy, at levels as low as three
drinks per week, is associated with an increased incidence of spontaneous
pregnancy loss (204–206). Cigarette smoking has been linked to early
spontaneous pregnancy loss; however, this is not without controversy (207–
209). Alcohol and tobacco intake in the male partner correlates with the
incidence of domestic violence, which in turn is associated with early
pregnancy loss (210). Marijuana has not been shown to necessarily increase
the risk of miscarriage in the one study investigating association found in the
literature to date (370), however studies have shown poor effects on female
(371) and male (372) fertility and patients should be counseled to refrain
until further studies can evaluate risk further. Evidence adds to a growing
body of literature that suggests consumption of coffee and other caffeinated
beverages during early pregnancy is linked to adverse pregnancy outcomes
(207,211). One report casts doubt on the definition of a lower limit for safe use of
caffeine in the first trimester of pregnancy (207).
Maintaining a healthy weight may decrease risk of miscarriage as being
underweight (373) and overweight (374) have been associated with increased risk
of miscarriage. Risk of sporadic and recurrent miscarriage are increased with
obesity and etiologic theories include impact on both gamete quality and uterine
receptivity in autologous conception (375) and donor egg pregnancies (212).
PRECONCEPTION EVALUATION
[4] Investigative measures that are potentially useful in the evaluation of recurrent
spontaneous miscarriage include obtaining a thorough history from both partners,
performing a physical assessment of the woman (with attention to the pelvic
examination), and a limited amount of laboratory testing (Table 33-2).
Table 33-2 Investigative Measures Useful in the Evaluation of Recurrent Early
Pregnancy Loss
1989History
1. Pattern, trimester, and characteristics of prior pregnancy losses
2. History of subfertility or infertility
3. Menstrual history
4. Prior or current gynecologic or obstetric infections
5. Signs or symptoms of thyroid, prolactin, glucose tolerance, and hyperandrogenic
disorders (including polycystic ovarian syndrome)
6. Personal or familial thrombotic history
7. Features associated with the antiphospholipid syndrome (thrombosis, false positive
test for syphilis)
8. Other autoimmune disorders
9. Medications
10. Environmental exposures, illicit and common drug use (particularly caffeine,
alcohol, cigarettes, marijuana, and in utero diethylstilbestrol exposure)
11. Genetic relationship between reproductive partners
12. Family history of recurrent spontaneous abortion, of obstetric complications, or of
any syndrome associated with embryonic or fetal losses
13. Previous diagnostic tests and treatments, including, if available, chromosome
testing on products of conception
Physical Examination
1. General physical examination with attention to:
a. Obesity
b. Hirsutism/acanthosis
c. Thyroid examination
d. Breast examination/galactorrhea
e. Pelvic examination
1. Anatomy
2. Infection
3. Trauma
4. Estrogenization
5. Masculinization
Laboratory
19901. Parental peripheral blood karyotype (both partners)
2. Chromosome testing on products of conception
3. Hysterosalpingography, three-dimensional transvaginal sonography,
sonohysterography, or office hysteroscopy, followed by hysteroscopy/laparoscopy, if
indicated
4. Serum thyroid stimulating hormone level
5. Serum prolactin level
6. Serum HbA1c
7. Antiphospholipid screening
a. Anticardiolipin antibody levels (IgG and IgM)
b. Lupus anticoagulant (activated partial thromboplastin time or Russell viper
venom)
c. Anti-β2-glycoprotein-1 antibodies (IgG and IgM)
History
A description of all prior pregnancies, their sequence and whether histologic
assessment and karyotype determinations were performed on previously aborted
tissues are important aspects of the history. Approximately 60% of pregnancies
lost before 8 weeks of gestation are reported to be chromosomally abnormal;
most of these pregnancies are affected by some type of trisomy, particularly
trisomy 16 (215,216). The most common single chromosomal abnormality is
monosomy X (45X), especially among anembryonic conceptuses (217).
Aneuploid losses are particularly prevalent among women with recurrent
pregnancy loss who are over the age of 35 (8). Research suggests a higher rate of
aneuploid miscarriage in recurrent pregnancy loss women with DOR at a younger
age (349). Although somewhat controversial, the detection of aneuploidy in
miscarriage specimens may be lower when the couple experiencing recurrent
miscarriages is euploidic. Alternatively, some investigators have suggested that,
because aneuploidy is common among miscarriage specimens from patients
experiencing isolated and recurrent spontaneous pregnancy losses, if aneuploidy
is documented in fetal tissues from a recurrent pregnancy loss patient, this loss
does not affect their prognosis for future pregnancy maintenance (13).
Most women with recurrent pregnancy loss tend to experience
spontaneous miscarriage at approximately the same gestational age in
sequential pregnancies (218). Unfortunately, the gestational age when
pregnancy loss occurs, as determined by last menstrual period, may not be
informative, because there is often a 2- to 3-week delay between fetal demise and
signs of pregnancy expulsion (219). If patients have had ultrasounds in the first
1991trimester, careful history and detailed record review can reveal a more accurate
time of fetal demise than gestational age by last menstrual period or patient’s
recall. The designation into either primary or secondary categories is not helpful
in the diagnosis or management of couples experiencing recurrent miscarriage.
Approximately 10% to 15% of couples cannot be classified into either the
primary or secondary category because, although their first pregnancy resulted in
a loss, it was followed by a term delivery prior to subsequent losses. Expert
groups exclude biochemical miscarriages, defined as positive pregnancy test but
miscarriage before ultrasound or histopathologic evidence can be obtained, from
guidelines. This recommendation is not without controversy. Biochemical
miscarriages can be distressing for patients and providers can feel obligated or
unsure about investigating further. Some evidence suggests women with recurrent
biochemical miscarriages or a mix of biochemical and clinical miscarriages have
similar poor prognosis for subsequent pregnancies (376,377). Investigation is
encouraged for recurrent clinical miscarriage (ultrasound or histopathologic
evidence) (338) but not biochemical miscarriages.
It is important to glean any history of subfertility or infertility among
couples with recurrent pregnancy loss. This is defined as the inability to
conceive after 12 months of unprotected intercourse. By definition, 15% of
all couples will meet these criteria; this number increases to 33% among
couples with recurrent pregnancy losses. Because many pregnancies are lost
before or near the time of missed menses, subfertility among recurrent pregnancy
loss patients may, in some cases, reflect recurrent preclinical losses. Menstrual
cycle history may provide information about the possibility of oligo-ovulation or
other relevant endocrine abnormalities in recurrent pregnancy loss patients. A
personal and family history of thrombotic events or renal abnormalities may
provide vital information. A family history of pregnancy losses and obstetric
complications should be addressed specifically. Detailed information about drug
and environmental exposure should be obtained.
Physical Examination
A general physical examination should be performed to detect signs of
metabolic illness, including PCOS, diabetes, hyperandrogenism, and thyroid
or prolactin disorders. During the pelvic examination, signs of infection, DES
exposure, and previous trauma should be ascertained. Estrogenization of mucosal
tissues, cervical and vaginal anatomy, and the size and shape of the uterus should
be determined.
[4] Recommended Testing
1992[5] Laboratory assessment of couples with recurrent pregnancy losses should
include the following:
1. Chromosome analysis of the products of conception
2. Parental peripheral blood karyotyping with banding techniques
3. Assessment of the intrauterine cavity with either office hysteroscopy,
sonohysterography, three-dimensional transvaginal sonography, or
hysterosalpingography, followed by operative hysteroscopy if a
potentially correctable anomaly is found (220)
4. Thyroid function testing, including serum TSH levels
5. Anticardiolipin antibodies, anti-β2 glycoprotein-1 antibodies, and lupus
anticoagulant testing (aPTT or Russell viper venom testing)
6. Prolactin
7. HbA1c
Tests with Unproven Utility
A number of laboratory assessment tools are under investigation for use in
patients with a history of recurrent pregnancy loss. Results are either too
preliminary to warrant unfettered recommendation or studies of their use have
been too contradictory to allow final determination of their value.
Tests under investigation with evidence in favor of utilizing:
1. Evaluation of ovarian reserve using day 3 serum follicle–stimulating
hormone, estradiol, and anti-müllerian hormone levels. It appears that
decreased ovarian reserve may predict higher risk of aneuploid embryos
and miscarriage in all patients, including those with recurrent pregnancy
loss (64,65,349).
2. Testing for antithyroid antibodies among women with recurrent
pregnancy loss remains controversial, but is rapidly gaining support (52–
54,57,176–178). Investigators have demonstrated an increased prevalence
of these antibodies among women with a history of recurrent pregnancy
loss, even in the absence of thyroid endocrinologic abnormalities
(53,54,56,177).
3. Endometrial biopsy for plasma cells/chronic endometritis
Tests under investigation and the majority of research shows No clinical
benefit
a. Thrombophilia testing (FVL, prothrombin gene mutation, protein C
deficiency, protein S deficiency, antithrombin III deficiency,
homocysteine levels, MTHFR mutation). Once popular for patients with
1993recurrent pregnancy loss, evidence shows limited value in testing and or
treatment of thrombophilia testing to prevent miscarriage or poor
pregnancy outcome unless patients have a personal or family history of
thrombosis
b. Testing for peripheral evidence of TH1/TH2 cytokine dysregulation.
c. NK cell testing in peripheral blood or endometrium
d. Cervical cultures for mycoplasma, ureaplasma, and chlamydia may be
considered.
e. Testing for serologic evidence of PCOS using LH or androgen values may
be useful (43–46).
Tests not recommended for evaluation in patients with recurrent
pregnancy loss:
1. Evaluations that involve extensive testing for serum or site-specific auto- or
alloantibodies (including antinuclear antibodies and antipaternal cytotoxic
antibodies) are expensive and unproven. Their use often verifies the statistical
tenet that if the number of tests performed reaches a critical limit, the results of
at least one will be positive in every patient.
2. Testing for parental HLA profiles is never indicated in outbred populations.
Findings that HLA sharing is associated with poor pregnancy outcomes are
strictly limited to those specific populations studied, which have very high and
sustained levels of marriage within a limited community (179).
3. Use of mixed lymphocyte cultures has not proved useful. Use of other
immunologic tests is unnecessary unless these studies are performed, with
informed consent, under a specific study protocol in which the costs of these
experimental tests are not borne by the couple or their third-party payers.
4. Further work is necessary before suppressor cell or factor determinations,
cytokine, oncogene, and growth factor measurements, or embryotoxic factor
assessment can be clinically justified.
5. Endometrial biopsy for luteal phase defect
POSTCONCEPTION EVALUATION
Following conception, close monitoring of patients with histories of recurrent
pregnancy loss is advised to provide emotional support and to confirm
intrauterine pregnancy and its viability. Although controversial, some
studies recommend close monitoring in the first trimester of women with a
history of recurrent pregnancy loss resulting from a higher incidence of
ectopic pregnancy and complete molar gestation in this population (56,222–
226). Determining serum levels of a-hCG may be helpful in monitoring early
1994pregnancy until an ultrasonographic examination can be performed;
however, not all failing pregnancies will be preceded by inadequate a-hCG
levels (227). If used, serum a-hCG levels should be serially monitored from
the time of a missed menstrual period until the level is approximately 1,200
to 1,500 mIU/mL, at which time an ultrasonographic scan is performed and
blood sampling is discontinued. Other hormonal determinations are rarely of
benefit because levels are often normal until fetal death or miscarriage occurs
(228).
If a pregnancy has been confirmed, but clinical follow-up has met newly
defined criteria for a failed pregnancy (378), intervention is recommended to
expedite pregnancy termination and to obtain tissue for karyotype analysis. [9]
The importance of obtaining karyotypic analysis from tissues obtained after
pregnancy demise in a woman experiencing recurrent losses cannot be
overemphasized. Results may suggest karyotypic anomalies in the parents
and patients report their appreciation of receiving the information (379). The
documentation of aneuploidy may have important prognostic implications
and may direct future interventions. Cost analysis has demonstrated that
karyotypic analysis is financially prudent among patients with histories of
recurrent pregnancy loss (229). Analysis by traditional karyotype fails 20% to
40% of the time because of difficulties in growing cells from products of
conception and interpretation of results can be limited as a result of maternal cell
contamination (380). Techniques for analysis like comparative genomic
hybridization provide results in more than 90% of cases and can differentiate
46XX results from maternal cell contamination (230,380). This technology can be
used without fresh samples needed for cell growth and can even be used in
specimens that have been in formalin or paraffin (231).
In continuing pregnancies, first trimester screening using cell-free fetal DNA,
maternal chemistries, and fetal nuchal lucency measurement or chorionic villus
sampling is recommended for obstetrical indications. Amniocentesis may be
recommended to assess the fetal karyotype based on prior screening results. In the
future, fetal karyotype assessment may be performed using DNA isolated from
nucleated fetal erythrocytes in maternal blood (232) or from sampling of the
lower genital tract (381).
THERAPY
Advances in the treatment of patients with recurrent pregnancy loss have
been slow. Despite a rapid expansion in understanding the molecular and
subcellular mechanisms involved in implantation and early pregnancy
maintenance, extension of these concepts to prevention of recurrent early
1995pregnancy loss has lagged. Progress toward treatment of most causes of recurrent
pregnancy loss has been hampered by a variety of factors. The condition itself has
been inconsistently defined. The results of clinical trials involving recurrent
pregnancy loss patients are nearly impossible to compare and evaluate. Trial
design is frequently substandard, with lack of rationale, lack of appropriate
control groups, and poor statistical analysis, limiting the ability to draw concrete
conclusions from reported results. Epidemiologic data indicate that most patients
with a history of recurrent pregnancy loss will, in fact, have a successful
pregnancy the next time they conceive (7). For these reasons, with few
exceptions, most therapies for recurrent pregnancy loss must be considered
experimental. Until further study is completed, treatment protocols involving
these therapies should be undertaken only with informed consent and in the
setting of a well-designed, double-blind, placebo-controlled clinical trial.
[9] Common but controversial therapeutic options for patients with
recurrent pregnancy loss include the use of IVF with preimplantation
chromosomal screening of embryos, use of donor oocytes or sperm,
antithrombotic interventions, the repair of anatomic anomalies, the
correction of any endocrine abnormalities, the treatment of infections, and a
variety of immunologic interventions and drug treatments. Treatment for
patients with recurrent miscarriage should include close monitoring of
pregnancy, psychological counseling and support, and karyotypic analysis of
tissues from subsequent miscarriage.
Genetic Abnormalities
Evidence suggests that, in women with a history of three or more spontaneous
pregnancy losses, a subsequent pregnancy loss has a 58% chance of chromosomal
abnormality (382). Among women with recurrent pregnancy loss who are age 35
or older, the aneuploidy rate is much higher at 80% (8). Most chromosomal
abnormalities identified in miscarriages are autosomal trisomies and considered to
result from maternal nondisjunction. Maternal age appears as a consistent and
important risk factor for trisomy in most studies. DOR can be associated with
higher aneuploidy rate in young women with recurrent pregnancy loss (349).
There are several options for patients who suffer from recurrent pregnancy loss
who have an identified miscarriage caused by trisomy. The first is to conceive
again without any specific change in medical management, as these abnormalities
are sporadic and unlikely to recur. Studies examining patients with recurrent
pregnancy loss show that women who miscarry chromosomally abnormal
conceptions are more likely to achieve a live birth with subsequent pregnancy
than those who miscarry chromosomally normal conceptions (13,233). A second
treatment option is chromosomal screening of embryos before implantation,
1996commonly referred to as preimplantation genetic screening (PGS), and a third
option involves the use of donor gametes.
Because chromosomal abnormalities are the most commonly identified cause
of miscarriage, some have argued that the use of chromosomal screening of
embryos is indicated for patients with recurrent pregnancy loss. This technique
involves biopsying a single cell from a cleavage stage embryo (day 3) or many
labs are biopsying several cells from blastocysts (day 5 or 6). Genetic testing can
be performed on these cells to determine abnormalities in chromosome number
and morphology. Embryos that are diagnosed with genetic abnormalities would
be discarded and only those embryos with euploid results considered appropriate
for transfer into the uterus. The biopsying of cells from embryos to screen for
specific disease causing mutations like cystic fibrosis or sickle cells disease,
commonly referred to as preimplantation genetic diagnosis (PGD), is used in
many internationally recognized assisted reproductive technology centers,
however the use of chromosomal screening via biopsying embryos remains
controversial, especially for recurrent pregnancy loss patients.
The use of chromosomal screening of embryos has the potential to reduce the
incidence of pregnancy loss arising from a chromosome issue within the embryo.
However, definitive studies in this population have not yet been done. The use of
this technology requires the patient to undergo an IVF cycle to obtain embryos for
biopsy at significant cost and medical intervention. Although there are several
retrospective studies showing reduced miscarriage rates with this technique,
several prospective trials using the outcome of successful pregnancy per started
cycle fail to show significant benefit (234–244). IVF is invasive and costly and
many patients with recurrent pregnancy loss conceive quickly without
intervention and have a high likelihood of live birth with their subsequent
pregnancy. Therefore, the optimal control group for a study of IVF with
chromosomal screening in the recurrent pregnancy loss population is debated.
Should it be natural conceptions or IVF without testing of embryos? Finally, the
prognosis for a patient with recurrent pregnancy loss does seem to be linked to the
chromosome analysis of prior miscarriages. Recurrent pregnancy loss patients
who miscarry chromosomally abnormal embryos, seem to have better prognosis
than those who miscarry chromosomally normal conceptions, again arguing for
expectant management for recurrent pregnancy loss patients with a history of
aneuploid loss. On the other hand, patients with poorer prognosis are those who
miscarry chromosomally normal embryos and therefore would not benefit from
IVF and chromosomal screening of embryos. One intent to treat analysis showed
similar pregnancy outcomes in recurrent pregnancy loss patients who chose
expectant management compared to those who chose IVF with chromosomal
screening (383). The efficacy of chromosomal screening of embryos in the
1997treatment of patients with recurrent pregnancy loss continues to be investigated,
and the methods of embryo biopsy and genetic testing continue to evolve
(242,243). As these techniques improve and the understanding of aneuploidy and
recurrence improves, there may be a subset of recurrent pregnancy loss patients,
such as carriers of parental translocations, who might benefit from this
intervention. IVF with chromosomal screening of embryos can be considered, but
not strongly recommended, for patients with recurrent pregnancy loss.
An additional option for patients with recurrent miscarriage is the use donor
eggs or sperm. This treatment is useful for recurrent pregnancy loss patients with
specific parental genetic factors and couples with DOR. Patients with
robertsonian translocations involving homologous chromosomes have a genetic
anomaly which always results in unbalanced gametes, and the use of donor
oocyte or donor sperm is recommended. Use of donor gametes among patients
with a history of recurrent pregnancy loss can be useful in other cases where
couples are at higher risk for unbalanced offspring because one or both
prospective parents carries other chromosomal rearrangements, such as reciprocal
translocations. In these cases, use of donor gametes was demonstrated to be as
effective as its use in matched patients without such a history (245). In all cases of
balanced translocations or embryonic aneuploidy, genetic counseling is
recommended. Couples with DOR and/or advanced reproductive age have a
higher risk of miscarriage, aneuploidy (349), and limited success with IVF with
chromosomal screening and therefore should be counseled about the option of
using donor eggs.
Anatomic Anomalies
Hysteroscopic resection represents state-of-the-art therapy for submucous
leiomyomas, intrauterine adhesions, and intrauterine septa. Although its efficacy
has been debated, this approach appears to limit postoperative sequelae while
maintaining improved reproductive outcomes (30,31,245–249). Use has been
safely extended to patients with DES exposure, hypoplastic uteri, and
complicated septal anomalies (30,31,250). Attempts to improve on standard
hysteroscopic metroplasty, which is typically performed in the operating room
using general anesthesia, often with laparoscopic guidance, are under
investigation. Ultrasonographically guided transcervical metroplasty is reported to
be safe and effective (246). Ambulatory, office-based procedures, including
septum resection under fluoroscopic or ultrasound guidance, are attractive options
(247).
For patients with a history of loss secondary to cervical incompetence,
placement of a cervical cerclage is indicated. This is usually performed early in
the second trimester after documentation of fetal viability. Cervical cerclage
1998should be considered as a primary intervention for women with DES-associated
uterine anomalies.
Endocrine Abnormalities
Some investigators have proposed the use of ovulation induction for the treatment
of recurrent pregnancy loss (248,249). The theory behind its use in these patients
rests on hypotheses that ovulation induction is associated with healthier oocytes.
Healthier oocytes, in turn, may decrease the incidence of luteal phase
insufficiency through a more receptive hormonal environment, which should
result in improved pregnancy maintenance. This approach grossly oversimplifies
the mechanisms involved in implantation and early pregnancy maintenance. Until
appropriately studied, use of empiric ovulation induction for treatment of
unexplained recurrent pregnancy loss should be viewed with caution. Evidence
from small studies indicates such use is not effective (248). Still, use of ovulation
induction in some subsets of patients with recurrent pregnancy loss could be of
benefit. For instance, stimulating folliculogenesis with ovulation induction or
luteal phase support with progesterone should be considered for women with
luteal phase insufficiency. The efficacy of these therapies, however, is not
substantiated (250). Ovulation induction might be beneficial for women with
androgen and LH hypersecretion disorders, especially following pituitary
desensitization with gonadotropin-releasing hormone agonist therapy (66). This
treatment remains controversial because the only large, prospective, randomized
controlled trial reports no therapeutic efficacy; none for prepregnancy pituitary
suppression nor for luteal phase progesterone supplementation (251).
Links between PCOS, hyperandrogenism, hyperinsulinemia, and recurrent
pregnancy loss make use of insulin-sensitizing agents in the treatment of recurrent
pregnancy loss associated with PCOS attractive (43–46). Although further study
is needed, there are an increasing number of reports that support its use for this
application (252,253). Prepregnancy glycemic control is particularly important for
women with overt diabetes mellitus (47,49). Thyroid hormone replacement may
be helpful in cases of hypothyroidism. There are data indicating that thyroid
hormone therapy may be of some benefit in euthyroid recurrent loss patients with
antithyroid antibodies and possibly even in all pregnant women with “euthyroid”
TSH levels between 2.5 and 5.0 mIU/L (52–54,177). Use of dopamine agonists to
normalize prolactin levels in patients with recurrent pregnancy loss has improved
subsequent pregnancy outcomes in limited studies (63), but remains controversial
(384). There does not appear to be a place in the medical management of
recurrent pregnancy loss for administering bromocriptine to women who do not
have a prolactin disorder.
1999Infections
Empiric antibiotic treatment has been used for couples with recurrent miscarriage
but its efficacy is unproven. Elaborate testing for infectious factors among
recurrent pregnancy loss patients and use of therapeutic interventions is not
justified unless a patient is immunocompromised or a specific infection has been
documented (67). For cases in which an infectious organism has been identified,
appropriate antibiotics should be administered to both partners, followed by
posttreatment culture to verify eradication of the infectious agent before
attempting conception.
Chronic endometritis, defined as the asymptomatic presence of histologically
documented plasma cells in an endometrial biopsy, may be associated with
recurrent miscarriage. In suspected cases of chronic endometritis, it is difficult to
determine cause and effect but treatment with antibiotics shows a higher live birth
rate in subsequent pregnancies in some studies (353,354). Treatment for chronic
endometritis is not recommended by expert groups and larger studies are needed
before implementing evaluation and treatment in routine practice.
Immunologic Factors
[5] Immune-mediated recurrent pregnancy loss has received more attention than
any other single etiologic classification of recurrent pregnancy loss. Nevertheless,
the diagnosis and subsequent treatment of the majority of cases remain unclear
(56,118,254–256). Most therapies for proposed immune-related recurrent
pregnancy loss can have harmful side effects and must be considered
experimental.
Immunostimulating Therapies: Leukocyte Immunization
Stimulation of the maternal immune system using alloantigens on either paternal
or pooled donor leukocytes has been promoted for patients with immunologic
recurrent pregnancy loss, but data do not support its use and side effects can be
dangerous. One of the largest trials evaluating the efficacy of leukocyte
immunization in patients with unexplained recurrent pregnancy loss is a part of
the Recurrent Miscarriage (REMIS) study (258). This investigation was large
(over 90 patients per treatment arm), prospective, placebo controlled, randomized,
and double blinded. It demonstrated no efficacy for paternal leukocyte
immunization in couples with unexplained recurrent pregnancy loss. The best of
the meta-analyses definitively rejects use of this therapy in patients with recurrent
loss (259). Leukocyte immunization poses a significant risk to the mother and her
fetus (231,232,260). Several cases of graft-versus-host disease, severe intrauterine
growth retardation, and autoimmune and isoimmune complications have been
2000reported (257,260–264). Alloimmunization to platelets contained in the paternal
leukocyte preparation is associated with cases of potentially fatal fetal
thrombocytopenia. The routine use of this therapy for recurrent miscarriage is not
clinically justified.
Other immunostimulating therapies have been proposed and abandoned.
Intravenous preparations consisting of syncytiotrophoblast microvillus plasma
membrane vesicles have been used to mimic the fetal cell contact with maternal
blood that normally occurs in pregnancy (265). The efficacy of this therapy has
not been established (259,265,266). The use of third-party seminal plasma
suppositories has been attempted, based on the misconception that TLX was part
of an idiotype–anti-idiotype control system (267,268). Third-party seminal
plasma suppositories for recurrent miscarriage have no scientifically credible
rationale and should not be used.
Immunosuppressive Therapies
Immunosuppressive and other immunoregulating therapies have been advocated
for cases in which miscarriage was believed to result from antiphospholipid
antibodies or inappropriate cellular immunity toward the implanting fetus. Study
design problems, including small numbers of recruited patients, lack of
prestratification by maternal age and number of prior losses before randomization,
and other methodologic and statistical inaccuracies preclude definitive statements
regarding therapeutic efficacy for most of the proposed immunosuppressive
approaches.
Intravenous Immunoglobulin
Intravenous immunoglobulins (IVIgs) are composed of pooled samples of
immunoglobulins harvested from a large number of blood donors. Studies on the
use of IVIg therapy in the treatment of recurrent pregnancy loss are based on the
theory that some recurrent pregnancy loss patients have an overzealous immune
reactivity to their implanting fetus. IVIgs do have immunosuppressive effects, but
the mechanisms underlying this immune modulation are only partially
understood. Based on a large number of relatively small studies using a variety of
treatment protocols, there remains no conclusive evidence to suggest that use of
IVIg in the treatment of patients with unexplained (and presumed immunologic)
recurrent pregnancy loss has any benefit (261,269–273). This includes a recent
trial using IVIg in women with secondary recurrent pregnancy loss that was
ended early because interim analyses revealed no effect (269). The Cochrane
review of immune therapy for recurrent pregnancy loss addressed IVIg therapy
and reported that its use did not alter pregnancy outcomes in patients with
otherwise unexplained recurrent pregnancy loss (259,266). Improved
2001posttreatment pregnancy rates may be seen, however, when IVIg is used in those
specific patients with autoimmune-mediated pregnancy loss associated with APS
(274,275). Therapy with IVIgs for recurrent pregnancy loss is expensive,
invasive, and time-consuming, requiring multiple intravenous infusions over the
course of pregnancy (276). Use of IVIgs for recurrent pregnancy loss is not
supported by current evidence and may result in significant side effects such as
nausea, headache, myalgias, and hypotension (262). More serious adverse effects
include anaphylaxis (particularly in patients with IgA deficiency) (277).
Progesterone
As mentioned earlier, progesterone has known immunosuppressive effects and
empiric progesterone supplements for women with a history of recurrent
pregnancy loss is a relatively common practice (129–132,136,137). A number of
studies using in vitro cellular systems relevant to the maternal–fetal interface have
demonstrated that progesterone either inhibits TH1 immunity or causes a shift
from TH1- to TH2-type responses that are more favorable for successful
pregnancies (136,137,278). Clinical trials evaluating progesterone use in recurrent
miscarriage patients show varying results. In 2013, a Cochrane review of multiple
studies showed a benefit of progesterone supplementation in women with
recurrent pregnancy loss; however, the studies differed in sample size, timing,
dose, and type of progesterone supplementation (385). In 2015, Coomarasamy et
al. performed a randomized controlled trial of vaginal progesterone in women
with three or more first trimester miscarriages. Women were randomized to 400
mg vaginal micronized progesterone twice daily or matched placebo starting with
positive pregnancy test but no later than 6 weeks of gestation (386). Similar live
birth rates were achieved in the two groups and arguments against routine
progesterone use in recurrent pregnancy loss patients could be made despite the
late start of progesterone (up to 6 weeks gestation) in some patients. Some
research suggests an earlier start to progesterone supplementation is beneficial for
outcomes despite the side effects of luteal phase progesterone, including delayed
onset of menses, which can be distressing for women trying to conceive (387).
Progesterone has been administered intramuscularly and intravaginally for the
treatment of recurrent pregnancy loss. It is thought that vaginal administration
may increase local, intrauterine concentrations of progesterone better than
systemic administration. Vaginal formulations may provide a better method of
attaining local immunosuppressive levels of progesterone while decreasing
adverse systemic side effects.
Intralipid Infusion
The relative paucity of inflammatory diseases among the Greenland Inuit
2002population, who consume a diet high in fish oils, led investigators to study the
immune modulatory effects of lipid emulsions in total parenteral nutrition
preparations for preoperative patients and for burn and trauma victims (279–282).
The wide range of demonstrated effects, including lipid preparations that reduced
NK cell activity, reduced monocyte proinflammatory cytokine production and
increased susceptibility to infection, led investigators to hypothesize, as early as
1994, that lipid infusions might promote an immune environment that would
favor pregnancy maintenance (283). Since that time, a small number of
publications have addressed the effects of lipid infusions (intralipids) in women
with a history of pregnancy loss (284,285). These investigations have
demonstrated a decrease in peripheral NK cell activity in women treated with one
to three infusions of intralipids. This effect lasted from 4 to 9 weeks after the last
infusion (284). The authors did not address NK cell cytokine secretion patterns
nor did they assay decidual NK cell function. Despite this paucity of data,
intralipid infusions are being administered to recurrent pregnancy loss patients
with increasing frequency. The existing data do not support this practice and side
effects can include flushing, dizziness, myalgias, nausea, anaphylactic reactions,
kidney and liver dysfunction, infection, and thrombosis. Intralipid infusions in
recurrent pregnancy loss patients is not recommended clinically and should be
administered only under an institutional review board–approved protocol and in a
study setting.
TNF-α Inhibition
Interest in the potent proinflammatory cytokine, TNF-α, as a mediator of
pregnancy loss came out of the description of the TH1 and TH2 paradigm (125).
There have been several publications that link maternal serum TNF-α levels and
activating TNF-α gene promoter polymorphisms to recurrent pregnancy loss
(286–288). The development of antagonists of TNF-α in the form of blocking
antibodies (adalimumab, infliximab) and inhibitory recombinant proteins
(etanercept) has permitted successful treatment of several autoimmune disorders,
including rheumatoid arthritis, psoriasis, and Crohn disease. Their use has not
been associated with universally positive outcomes and may worsen some
disorders, including multiple sclerosis (289). These products are associated with
rare but worrisome side effects, including liver failure, aplastic anemia, interstitial
lung disease, and anaphylaxis (290). Although there exists only a single, small,
retrospective, observational, nonrandomly assigned case series that involved
treatment of recurrent pregnancy loss patients with inhibitors of TNF-α, these
positive preliminary results have led a growing number of clinics to offer this
therapy to patients, often at a significant cost (291). The safety of these
compounds in pregnancy has not been appropriately studied and preliminary
2003reports associating exposure to TNF-α inhibitors during early pregnancy to fetal
VACTERL syndrome is concerning (292). As with intralipid therapy, use of
TNF-α inhibition for the treatment of recurrent pregnancy loss should be
implemented only under an institutional review board–approved protocol in a
study setting and should not generate clinical income.
Other immunoregulating therapies theoretically useful in treating recurrent
pregnancy loss include the use of cyclosporine, pentoxifylline, and nifedipine,
although maternal and fetal risks with these agents preclude their clinical use.
Plasmaphoresis has been used to treat women with recurrent miscarriage and
antiphospholipid antibodies (293). Generalized immunosuppression with
corticosteroids, such as prednisone, has been advocated during pregnancy for
women with recurrent losses and chronic intervillositis and those with recurrent
pregnancy loss and APS (294). Although corticosteroids have shown some
treatment promise in these patients, maternal and fetal side effects, such as
gestational diabetes and intrauterine growth restriction, and the availability of
alternative therapies have limited their use (294,295). The efficacy and side
effects of prednisone plus low-dose aspirin was examined in a large, randomized,
placebo-controlled trial treating patients with autoantibodies and recurrent
pregnancy losses. Pregnancy outcomes for treated and control patients were
similar; however, the incidence of maternal diabetes and hypertension and the risk
of premature delivery were all increased among those treated with prednisone and
aspirin (296).
Antithrombotic Therapy
Therapy for patients with recurrent pregnancy losses associated with APS has
shifted toward the use of antithrombotic medications. Unlike immunosuppressive
treatments, this approach appears to address the effect (hypercoagulability), but
not the underlying cause (e.g., genetic, APS) of recurrent pregnancy loss. There
are reports that heparin, one typical anticoagulant, may exert direct
immunomodulatory effects by binding to antiphospholipid antibodies and may
decrease movement of inflammatory cells to sites of alloantigen exposure
(297,298). The combined use of low-dose aspirin (75 to 81 mg per day) and
subcutaneous unfractionated heparin (5,000 to 10,000 units twice daily) during
pregnancy has been best studied among women with APS and appears to be
efficacious (299–303). A typical regimen for women with antiphospholipid
syndrome would include use of aspirin (81 mg every day) beginning with any
attempts to conceive. After pregnancy has been confirmed, 5,000 IU
unfractionated sodium heparin is administered subcutaneously twice daily,
throughout gestation. Patients using this therapy should be treated in conjunction
with a perinatologist because of their increased risks for preterm labor, premature
2004rupture of the membranes, intrauterine growth restriction, intrauterine fetal
demise, and preeclampsia. Other potential risks include gastric bleeding,
osteopenia, and abruptio placenta.
Attempts have been made to extend the finding that antithrombotic therapy is
efficacious when used to treat patients with APS and recurrent pregnancy loss.
These attempts include the use of low–molecular-weight heparins (LMWHs), the
use of antithrombotic therapy in non-APS patients with thrombophilia and
recurrent pregnancy loss, and even its use among recurrent pregnancy loss
patients without thrombophilia (unexplained recurrent losses).
New formulations of heparin, termed LMWHs, have been demonstrated to
be superior to unfractionated heparin in the treatment of many clotting
disorders (304–306). LMWH has the advantage of an increased antithrombotic
ratio when compared with unfractionated heparin. This results in improved
treatment of inappropriate clotting with fewer bleeding side effects and LMWH
has been associated with a decreased incidence of thrombocytopenia and
osteoporosis when compared with its unfractionated counterpart. LMWH has a
long half-life and requires less frequent dosing and monitoring, thereby
improving patient compliance. LMWH appears to be safe for use in
pregnancy, and has shown promise when combined with low-dose aspirin in
the treatment of recurrent pregnancy loss associated with APS (300,305,307).
A few studies have compared the use of unfractionated heparin and aspirin to
LMWH and aspirin in the treatment of women with APS and adverse pregnancy
outcomes (303,308). The therapies had similar effects in one study (308). A metaanalysis suggested that unfractionated heparin was superior to LMWH, however,
there was significant heterogeneity between studies (303).
Anticoagulation for recurrent pregnancy loss patients with thrombophilia but
no personal or family history of thrombosis is controversial. Early studies showed
efficacy for LMWH treatment for patients with recurrent pregnancy loss
associated with other thrombophilias, including activated protein C resistance
associated with FVL, mutations in the promoter region of the prothrombin gene,
and decreases in protein C and protein S activities (309–311,317). The use of
LMWH for this indication appears to have a reassuring safety profile for mother
and fetus (307,312,313). Studies and expert groups argue that, despite the
biologic plausibility that patients with recurrent pregnancy loss would have a
higher chance of inherited thrombophilia and that anticoagulation of patients with
these diagnoses would decrease risk of subsequent miscarriage, the evidence does
not support the theories (338,341).
The prophylactic use of daily low-dose aspirin has become common practice
within the lay public based on its perceived cardiovascular effects combined with
its low incidence of side effects. Its sole use in the treatment of recurrent
2005pregnancy loss has likewise gained momentum, and many patients with histories
of recurrent loss will either be self-prescribing this therapy or will inquire about
its usefulness. There are no good data supporting its use either in patients with
heritable thrombophilias or in the general recurrent pregnancy loss population.
Although studies are small, the use of low-dose aspirin alone has not been shown
to be effective in the treatment of recurrent pregnancy loss associated with APS
(301,314,315). When used in these patients, it should be in combination with
unfractionated or LMWH. Large randomized prospective trials examining the
empiric use of aspirin alone or in combination with prophylactic doses of heparin
have shown no benefit of these therapies in unexplained recurrent pregnancy loss
(315). The use of aspirin in early pregnancy has been called into question with
reports of an increased incidence of isolated spontaneous pregnancy loss among
women who used this medication (213,214). These reports are poorly designed
and do not adequately address the level of aspirin exposure 81 mg versus 325 mg.
Although reviews have touted the overall safety of aspirin in pregnancy, outside
of use in combination with heparin for patients with recurrent pregnancy loss and
APS, this medication should be used only with justification in the well-informed
patient during early pregnancy (316).
As mentioned previously, vitamins B6, B12, and folate are important in
homocysteine metabolism, and hyperhomocysteinemia is linked to recurrent
pregnancy loss in some studies (15,17,27,388). Women with recurrent pregnancy
loss and isolated fasting hyperhomocysteinemia should be offered supplemental
folic acid (0.4 to 1.0 mg per day), vitamin B6 (6 mg per day), and possibly
vitamin B12 (0.025 mg per day) (318–321). Fasting homocysteine levels should
be retested after treatment. If levels are normalized or remain only marginally
elevated, no further therapy is necessary. Homocysteine levels will predictably
decrease during pregnancy.
Treatment of women with recurrent pregnancy loss and an identified
inherited or acquired thrombophilia should be based on accompanying
history. There are no published large prospective controlled trials examining the
benefit of anticoagulation for the prevention of miscarriage in the absence of
APS, and, therefore, anticoagulation recommendations for patients with inherited
thrombophilias are based on individualized risk of venous thromboembolic events
in pregnancy (16).
If a venous thromboembolic event occurs during the index pregnancy,
posthospitalization management requires therapeutic anticoagulation.
UFH: 10,000 to 15,000 U subcutaneous every 8 to 12 hours (monitor to
keep aPTT 1.5 to 2.5 times normal) OR
2006LMWH: enoxaparin 40 to 80 mg subcutaneous twice a day or
dalteparin 5,000 to 10,000 U subcutaneous twice a day). Consider
monitoring trough factor Xa levels in the third trimester.
If there is a personal history of venous thromboembolic events
(particularly in a previous pregnancy or with hormonal contraceptive
use) or a strong thrombophilic family history, treat with therapeutic
anticoagulation. Thrombotic risk is greatest during the postpartum
period.
Anticoagulation should be reinitiated after delivery in doses reflecting
predelivery treatment regimens. Postpartum anticoagulation should be
continued for 6 to 12 weeks postpartum (305). Women may continue
injectable therapy or transition to oral anticoagulants (e.g., coumarin). Use
of heparin or of coumarin derivatives does not prohibit breastfeeding.
Psychological Support
There is no doubt that experiencing isolated and recurrent losses can be
emotionally devastating. The risk of major depression is increased greater than
twofold among women with spontaneous pregnancy loss; in most women it arises
in the first weeks following delivery (322). A caring and empathetic attitude is
prerequisite to all healing. Acknowledgment of the pain and suffering couples
have experienced because of recurrent miscarriage can be a cathartic catalyst
enabling them to incorporate their experience of loss into their lives rather than
focusing their lives on their experience of loss (66). Referrals to support groups
and counselors should be offered. Self-help measures, such as meditation, yoga,
exercise, and biofeedback may also be useful.
PROGNOSIS
[7] The prognosis for successful pregnancy depends on the potential underlying
cause of pregnancy loss and (epidemiologically) on the number of prior losses.
Epidemiologic surveys indicate that the chance of a viable birth even after four
prior losses may be as high as 60%. Depending on the study, the prognosis for
successful pregnancy in couples with a cytogenetic etiology for reproductive
loss varies from 20% to 80% (323–325). Women with corrected anatomical
anomalies may expect a successful pregnancy in 60% to 90% of cases
(28,323,326–329). A success rate higher than 90% has been reported for
women with corrected endocrine abnormalities (324). Between 70% and
90% of pregnancies reported among women receiving therapy for
antiphospholipid antibodies have been viable (330,331).
Many forms of pre- or postconceptional tests have been proposed to help
2007predict pregnancy outcome (221,332,333,389); none have been fully
substantiated in large, prospective trials. The documentation of fetal cardiac
activity on ultrasound may offer prognostic value; however, it appears that
its predictions may be greatly affected by any underlying diagnosis. In one
study, the live birth rate following documentation of fetal cardiac activity between
5 and 6 weeks from the last menstrual period was approximately 77% in women
with two or more unexplained spontaneous miscarriages (334). It may be
important to note that most of the patients in this study had evidence of
inappropriate antitrophoblast cellular immunity. Others have shown that 86% of
patients with antiphospholipid antibodies and recurrent pregnancy loss had fetal
cardiac activity detected prior to subsequent demise (335). A prospective,
longitudinal, observational study of 325 patients with unexplained recurrent
pregnancy losses demonstrated that only 3% of 55 miscarriages occurred
following the detection of fetal cardiac activity using transvaginal
ultrasonography (336). The majority of couples with recurrent pregnancy loss
will go on to have live birth and reminding patients of this throughout evaluation
and treatment can be an invaluable tool for psychological and emotional support
through the process
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