Hemorrhagic Placental Disorders
BS. Nguyễn Hồng Anh
Hemorrhage ollowing partial or complete separation o the placenta can be torrential. Recall that the amount o bloo owing through the intervillous space at term excees 600 mL/ min (Pates, 2010). In the secon hal o pregnancy, three placental isorers contribute substantially to maternal mortality rates. Tese inclue placental abruption, placenta previa, an placenta accreta spectrum.
Te contributions o hemorrhagic placental isorers to maternal mortality are iscusse in Chapter 1 (p. 7) an Chapter 42 (p. 733). Te management an clinical experience with these isorers span more than a generation. Placental abruption, or example, has been emphasize in this text or more than 50 years beginning with the work o Dr. Jack Pritchar. Now more common than years past, placenta accreta spectrum is another substantial threat to maternal well-being
PLACENTAL ABRUPTION
■ Etiopathogenesis
Separation o the placenta—either partially or totally—rom its implantation site beore elivery is calle placental abruption or abruptio placentae. From Latin, the latter translates as “ren- ing asuner o the placenta,” which enotes a suen accient, which is characteristic o most cases. In the purest sense, the cumbersome—an thus selom use—term premature separation of the normally implanted placenta is most escriptive because it exclues separation o a placenta previa.
Abruption likely begins with rupture o a eciual spiral artery an hemorrhage into the eciual basalis. Te subsequent expaning retroplacental hematoma splits the eciua an leaves a thin layer aherent to the myometrium. Te eci- ual hematoma grows to lit away an compress the ajacent placenta. In some cases that are associate with preeclampsia, impaire trophoblastic invasion with subsequent atherosis is one unerlying preisposition (Brosens, 2011). Inammation or inection also may be contributory (Mhatre, 2016). However, histological nings cannot be use to etermine the timing o the abruption (Chen, 2017).
In the early stages o placental abruption, clinical symptoms may be absent. Even with continue bleeing an placental separation, placental abruption can still be either total or partial (Fig. 43-1). With either, bleeing typically insinuates itsel between the membranes an uterine wall, ultimately escaping through the cervix to cause external hemorrhage. Less oten, the bloo is retaine, leaing to concealed hemorrhage an elaye iagnosis. Te elay translates into greater maternal an etal hazars. With conceale hemorrhage, the likelihoo o consumptive coagulopathy is also increase. Tis is because increase pressure within the intervillous space, cause by the expaning retroplacental clot, orces more placental thromboplastin into the maternal circulation (Chap. 44, p. 775)
Most bloo in the retroplacental hematoma in a nontraumatic placental abruption is maternal. Tis is because hemorrhage erives rom separation within the maternal eciua, an placental villi are usually initially intact. In 78 women at Parklan Hospital with a nontraumatic placental abruption, etalto-maternal hemorrhage was ocumente in only 20 percent. All o these ha <10 mL etal bloo loss (Stettler, 1992). In another series o 68 women with a placental abruption, etal cells were oun in peripheral bloo in only 4 percent (Atkinson, 2015).
Placental abruption can create a visible circumscribe
epression on the maternal surace o a reshly elivere placenta. Tese epressions usually measure a ew centimeters in iameter an are covere by ark, clotte bloo. Because several minutes are require or these anatomical changes to materialize, a very recently separate placenta may appear totally normal at elivery. Our experiences are like those o Benirschke an associates (2012) in that the “age” o the retroplacental clot cannot be etermine exactly. In the example shown in Figure 43-2, a large ark clot is well orme. It has epresse the placental bulk an likely is at least several hours ol.
Dening placental abruption severity is problematic. We consier placental abruption severe when the etus ies. However, maternal an etal complications are requently serious even with a liveborn etus. Ananth an coworkers (2016) have ene severe placental abruption as isplaying one or more o the ollowing: (1) maternal sequelae that inclue isseminate intravascular coagulation (DIC), shock, transusion, hysterectomy, renal ailure, or eath; (2) etal complications such as nonreassuring etal status, growth restriction, or eath; or (3) neonatal outcomes that inclue eath, preterm elivery, or growth restriction.
Traumatic Abruption
External trauma—usually rom motor vehicle crashes or aggravate assault—can cause placental separation. Te requency o abruption originating rom trauma varies. Importantly, abruption can stem rom relatively minor trauma (Huls, 2018). Te clinical presentation an consequences o these abruptions ier somewhat rom spontaneous cases. For example, associate etomaternal hemorrhage, while selom clinically signicant with most spontaneous abruptions, is more common with trauma because o concomitant placental tears or “ractures” (Fig. 50-10, p. 895). In eight women with traumatic placental abruption care or at Parklan Hospital, we oun etal-to-maternal hemorrhage o 80 to 100 mL in three (Stettler, 1992). Importantly, in some cases o trauma, a nonreassuring etal heart rate tracing may not be accompanie by other evi- ence o placental separation. A sinusoial tracing is one example. Following blunt abominal trauma, uterine contractions are the single most important preictor o placental abruption (Greco, 2019). raumatic abruption is consiere in more etail in Chapter 50 (p. 894).
Chronic Abruption
When placental separation is not ollowe by elivery, the placental abruption is terme chronic. Some o these cases begin early in pregnancy. Dugo an coworkers (2004) observe an association between some abnormally elevate maternal serum aneuploiy markers an subsequent abruption. Others have correlate rst- an secon-trimester bleeing with thir- trimester placental abruption (Ananth, 2006; Weiss, 2004). In some cases, chronic abruption an oligohyramnios evelop an are calle the chronic abruption–oligohydramnios sequence (CAOS) (Elliott, 1998). Even later in pregnancy, hemorrhage with retroplacental hematoma ormation is occasionally arreste completely without elivery. Tese women may have abnormally elevate levels o maternal serum alpha-etoprotein (MSAFP) or placenta-specic RNAs as markers o the event (Miura, 2017; Ngai, 2012).
■ Frequency
Te reporte incience o placental abruption varies because o iering criteria use or iagnosis. Its requency averages 0.5 percent or 1 case in 200 eliveries. From one atabase o more than 125 million births rom 1979 through 2010, the incience o placental abruption was nearly 1 percent (Hill, 2020). In more than 250,000 eliveries at Parklan Hospital rom 2000 through 2015, the incience o placental abruption average 1 case in 290 births (Fig. 43-3).
Te requency o placental abruption has risen in this country, an most o this increase is in black women (Ananth, 2005, 2016). Tis isproportion may be explaine in part by the conservative management o early-onset preeclampsia in some institutions (Chap. 41, p. 714). At Parklan Hospital, however, the requency o severe placental abruption has ecline. Specically, with placental abruption so extensive as to kill the etus, the incience was 0.24 percent or 1 case in 420 births rom 1956 through 1967 (Pritchar, 1967). Trough 2020, this same requency roppe to 0.05 percent or 1 case in 2060 births. Tis likely reects a concurrent ecline in the number o high-parity women giving birth an rise in the availability o prenatal care an emergency transportation.
■ Perinatal Morbidity and Mortality
Overall, perinatal outcomes are inuence by gestational age, an the requency o placental abruption rises across the thir trimester. As seen in Figure 43-4, more than hal o the placental abruptions at Parklan Hospital evelope at gestational ages ≥37 weeks’ gestation. Perinatal mortality an morbiity, however, are more common with earlier abruptions an with concomitant preeclampsia (Furukawa, 2015; Han, 2019). O other relate actors, major etal congenital anomalies have greater association with placental abruption (Riihimäki, 2013).
Although the rates o etal eath have ecline, the contribution o abruption as a cause o stillbirth remains prominent because other causes also have ecrease. For example, since the early 1990s, 10 to 12 percent o all thir-trimester stillbirths at Parklan Hospital have been the consequence o placental abruption. In a review o more than 15 million singleton births between 1995 an 1998 in the Unite States, the perinatal mortality rate associate with placental abruption was 119 eath per 1000 births. Tis was higher than the rate o 8 eaths per 1000 births in the general obstetrical population (Salihu, 2005).
Neonatal eaths also are common ollowing placental abruption. At Parklan Hospital, 15 percent o liveborn neonates ie. Perinatal morbiity also is common in this group (Downes, 2017). Moreover, associate chilhoo mortality mainly stems rom birth-relate asphyxia an prematurity (Riihimäki, 2018). In one series, 20 percent o 43 liveborn neonates ha severe etal aciemia ollowing placental abruption, an 20 percent o survivors evelope cerebral palsy (Matsua, 2013). In another stuy o 84 liveborns, 29 (35 percent) ha an umbilical artery pH <7.00 (Onishi, 2019). Ananth an coworkers (2017) attribute some o the averse neuroevelopmental outcomes to preterm elivery.
■ Predisposing Factors
Demographic Factors
Several preisposing actors raise the placental abruption risk (Table 43-1). Advancing maternal age is one risk, although ata regaring women o great parity are conicting (see Fig. 43-3) (Okby, 2017). Race or ethnicity also appears important (Eubanks, 2021). In an earlier stuy, in almost 366,000 eliveries at Parklan Hospital, abruption severe enough to kill the etus was most common in black an white women—1 case in 200 births; less so in Asian women—1 in 300; an least common in Latinas—1 in 350 (Pritchar, 1991). A familial association was oun rom one Norwegian population-base registry (Rasmussen, 2009). In this stuy, i a woman ha a severe abruption, the risk or her sister was ouble. Caniate genes involve in mitochonrial biogenesis an oxiative phosphorylation pathways, which coner risk or placental abruption, have been escribe (Workalemahu, 2018).
Pregnancy-associated Hypertension
Some orm o hypertension is the most requent conition associate with placental abruption. Tis inclues gestational hypertension, preeclampsia, chronic hypertension, or a combination. Te hemolysis, elevate liver enzyme levels, low platelet count (HELLP) synrome carries an increase risk or placental abruption. Moreover, expectant management o preeclampsia in signicantly preterm pregnancies was complicate by placental abruption in 4 percent (Shoopala, 2019). In a report by Pritchar an colleagues (1991) that escribe 408 women with placental abruption an etal emise, hypertension was apparent in hal once hypovolemia was correcte. Hal o these latter women—a ourth o all 408—ha chronic hypertension. Examine another way, one Maternal-Fetal Meicine Units (MFMU) Network stuy oun that 1.5 percent o pregnant women with chronic hypertension suere placental abruption (Sibai, 1998). At Parklan Hospital, the placental abruption requency in women with treate chronic hypertension an signicant proteinuria was almost 1 percent. Tis incience compare with the 0.3-percent incience in women with treate hypertension without substantial proteinuria (Morgan, 2016).
Chronic hypertension with superimpose preeclampsia or with etal-growth restriction coners an even greater risk (Lueth, 2020). Even so, the severity o hypertension oes not necessarily correlate with abruption incience (Morgan, 2016; Zetterstrom, 2005). However, women with preeclampsia that experience placental abruption have worse maternal, etal, an neonatal outcomes compare with women experiencing abruption alone (Han, 2019). Te long-term eects o these associations are apparent rom the signicantly elevate cariovascular mortality risk in women with prior abruption, with or without chronic hypertension (DeRoo, 2016; Pariente, 2013).
Observations rom the Magpie rial Collaborative Group suggest that women with preeclampsia, with or without chronic hypertension, given magnesium sulate may have a reuce risk or abruption (Altman, 2002). Last, Roberge an colleagues (2018), perorme a metaanalysis an reporte that a 100-mg aily aspirin may ecrease the incience o placental abruption.
Preterm Prelabor Ruptured Membranes
Te placental abruption risk substantially rises when placental membranes rupture beore term. (Hackney, 2016). O 756 women with rupture membranes between 20 an 36 weeks’ gestation, 5 percent evelope an abruption (Major, 1995). Te requency was 17 percent with previable prelabor rupture membranes (Kibel, 2016). Te risk or abruption with preterm membrane rupture is urther elevate with comorbi inection (Ananth, 2004). In one cohort stuy o pregnancies ≥34 weeks’ gestation, the placental abruption rate was eightol higher i hyramnios was comorbi (Aviram, 2015). From a metaanalysis o 10 stuies that inclue term an preterm gestational ages, hyramnios was associate with a twool greater rate o placental abruption (Khazaei, 2019). Abrupt uterine ecompression uring membrane rupture may be an inciting actor.
Prior Abruption
Many o the preisposing actors in women with a history o an abruption are chronic conitions, an in these cases, placental abruption has a high recurrence rate. Women with abruption an etal eath have a recurrence rate o 12 percent, an hal o these abruptions cause another etal eath (Pritchar, 1970). Furuhashi an colleagues (2002) reporte a 22-percent recurrence rate, an hal recurre at a gestational age 1 to 3 weeks earlier than the rst abruption. In one longituinal Dutch stuy, Ruiter an coworkers (2015) cite a recurrence risk o 5.8 percent. In a population-base stuy o 767,000 pregnancies, the authors oun a sevenol higher risk or recurrence o a “mil” abruption an twelveol risk or a “severe” abruption (Rasmussen, 2009). For women who ha two severe abruptions, the risk or a thir was increase 50-ol.
Management o a pregnancy subsequent to an abruption is ifcult because another separation may suenly occur, even remote rom term. In many o these recurrences, evaluation o etal well-being is almost always reassuring beorehan. Tus, antepartum etal testing is usually not preictive. Because term abruptions ten to be recurrent, Ruiter an coworkers (2015) recommen labor inuction at 37 weeks’ gestation. It seems reasonable to inuce labor at 38 complete weeks i other complications o not evelop beorehan.
Other Associations
O these liste in able 43-1, cigarette smoking is linke to an elevate risk or placental abruption (Eubanks, 2021). One metaanalysis o 1.6 million pregnancies in smokers oun a twool risk (Ananth, 1999). Tis risk was ve- to eightol i smokers ha chronic hypertension, severe preeclampsia, or both. Similar nings are reporte by others (Hogberg, 2007; Kaminsky, 2007). Cocaine abuse is linke, an in one series o 50 women who abuse cocaine uring pregnancy, eight ha a stillbirth cause by placental abruption (Bingol, 1987).
Of potential serum markers, MSAFP, inhibin, an pregnancyassociate plasma protein in abnormal levels carry increase risk (Ananth, 2017). Inee, preliminary ata shows that MSAFP levels >280 µg/L in the thir trimester may be preictive (Ngai, 2012). Subclinical hypothyroiism or high levels o antithyroi antiboies have been associate with a two- to threeol higher risk or placental abruption (Abbassi-Ghanavati, 2010; Maraka, 2016). Lupus anticoagulant is associate with maternal oor inarction o the placenta but is less so with typical abruptions. Women aecte by some o the thrombophilias have higher associate rates o thromboembolic events uring pregnancy, however, no convincing evience supports a link between thrombophilias an placental abruption (American College o Obstetricians an Gynecologists, 2019; 2020).
■ Diagnosis
Te signs an symptoms o placental abruption can vary consierably. Classically, aecte women have a suen onset o abominal pain, vaginal bleeing, an uterine tenerness. In an earlier stuy, 78 percent ha vaginal bleeing, 66 percent ha uterine tenerness or back pain, an 60 percent ha a nonreassuring etal status (Hur, 1983). Other nings inclue requent contractions an persistent hypertonus. However, in a th, preterm labor was iagnose, an placental abruption was not suspecte until etal istress or eath ollowe.
In some women, external bleeing can be prouse, yet placental separation may not be so extensive as to compromise the etus. In others, external bleeing is absent, but the placenta is sufciently sheare o to kill the etus—a conceale abruption. In either case, bleeing can be massive an leas to hypovolemic shock. In an earlier report rom Parklan Hospital, Pritchar an Brekken (1967) escribe 141 women with abruption so severe as to kill the etus. Bloo loss in these women oten amounte to at least hal o their pregnant bloo volume.
Consumptive Coagulopathy
With placental abruption, some egree o intravascular coagulation is almost universal. Placental abruption is the most common cause o clinically prooun consumptive coagulopathy in obstetrics an probably in all specialties (Cunningham, 2015). A primary consequence o intravascular coagulation is the activation o plasminogen to plasmin, which then lyses brin microemboli to maintain microcirculatory patency. With placental abruption severe enough to kill the etus, pathological levels o brinogen–brin egraation proucts an d-imers are almost always oun in maternal serum (Erez, 2015). Teir quantication is not clinically useul.
In a thir o women with an abruption severe enough to kill the etus, the plasma brinogen level will be <150 mg/L. Tese levels are epenent on the maternal preabruption brinogen level, an thus higher levels are “protective” (Cunningham, 2015; Wang, 2016). Clinically signicant low levels may cause troublesome surgical bleeing, an measurement o levels assists brinogen-replacement eorts. Levels o several other coagulation actors also are variably ecrease. Tese are not specically measure in DIC, but actors are replace empirically with resh rozen plasma as a part o massive transusion protocols (Chap. 44, p. 772). In aition, thrombocytopenia, sometimes prooun, may accompany severe hypobrinogenemia an can be common ater repeate bloo transusions. Tis “ilutional coagulopathy” is aitive to DIC (Chap. 44, p. 772).
Consumptive coagulopathy is more likely with a conceale abruption because intrauterine pressure is higher. Tis orces more thromboplastin into the large veins raining the implantation site. With a partial abruption an a live etus, severe coagulation eects are less common. Our experience has been that i serious coagulopathy evelops, it is usually evient by the time abruption symptoms appear. In one unusual case, a woman care or at Parklan Hospital presente with a noseblee. She ha no pain or vaginal bleeing, but her etus was ea. Her bloo i not clot, an the plasma brinogen level was 25 mg/L. A total placental abruption was conrme at elivery.
Couvelaire Uterus
At the time o cesarean elivery, it is not uncommon to n wiesprea extravasation o bloo into the uterine musculature an beneath the serosa (Fig. 43-5). Tis phenomenon is name ater Couvelaire, who in the early 1900s terme it uteroplacental apoplexy. Tese myometrial hemorrhages may incite uterine atony, but are not a sole inication or hysterectomy. Eusions o bloo may collect beneath the tubal serosa, between the leaves o the broa ligaments, in the ovaries, or in the peritoneal cavity.
End-organ Injury
Acute kidney injury (AKI) is a general term escribing renal ys- unction rom many causes (Chap. 56, p. 1006). Delaye or incomplete treatment o hypovolemia is one. However, even with placental abruption complicate by severe DIC, prompt an vigorous treatment with bloo an crystalloi solutions usually prevents signicant renal ysunction. Te risk or renal injury with placental abruption rises when preeclampsia coexists (Alexaner, 2015; Drakeley, 2002). Most cases o AKI are reversible, o not require ialysis, an generally have goo long-term outcomes (Arazi, 2015). However, irreversible acute cortical necrosis occasionally stems rom placental abruption (Gopalakrishnan, 2015).
Rarely, pituitary ailure—Sheehan syndrome—ollows severe intrapartum or early postpartum hemorrhage. Describe in Chapter 61 (p. 1104), the exact pathogenesis is not well unerstoo, especially because enocrine abnormalities are inrequent even in women who suer catastrophic hemorrhage (Matsuwaki, 2014).
Differential Diagnosis
Severe placental abruption usually is obvious. However, less severe orms are not always recognize with certainty, an the iagnosis becomes one o exclusion. Unortunately, no laboratory tests or other iagnostic methos accurately conrm lesser egrees o placental separation. Sonography has limite use because the placenta an resh clots may have similar imaging characteristics. In a stuy o 149 women with a suspecte placental abruption, the sensitivity or sonography was only 24 percent (Glantz, 2002). Tus, negative nings with sonographic examination o not exclue placental abruption.
Conversely, magnetic resonance (MR) imaging is highly sensitive or placental abruption an shoul be consiere i the iagnostic inormation woul change management (Masselli, 2011). Last, elevate serum levels o d-imers may be suggestive, but this has not been aequately teste. Tus, in the woman with vaginal bleeing an a live etus, placenta previa an other bleeing causes are sought with clinical an sonographic evaluation. It has long been taught— perhaps with some justication—that painul uterine bleeing signies placental abruption, whereas painless uterine bleeing inicates placenta previa. Te ierential iagnosis is usually not this straightorwar, an labor accompanying previa may cause pain that suggests placental abruption. Conversely, pain rom placental abruption may mimic normal labor, or it may be painless, especially with a posterior placenta. At times, the vaginal bleeing source remains obscure even ater elivery.
■ Management
reatment varies epening on maternoetal clinical conition, gestational age, an amount o associate hemorrhage. With a living viable-age etus an with vaginal elivery not imminent, emergency cesarean elivery is chosen by most. In some women, etal compromise will be evient as shown in Figure 43-6. When evaluating etal status, sonographic conrmation o etal heart activity may be necessary because sometimes an electroe applie irectly to a ea etus will provie misleaing inormation by recoring the maternal heart rate (Chap. 24, p. 447).
I the etus has ie or i it is not consiere sufciently mature to live outsie the uterus, vaginal birth is preerable or the mother. In either case, prompt an intensive resuscitation with bloo proucts an crystallois is begun. Tese measures are liesaving or the mother an hopeully or her etus. I the iagnosis o placental abruption is uncertain an the etus is alive an without evience o compromise, close observation may be warrante provie that immeiate intervention is available. Colón an coworkers (2016) perorme a ranomize trial an oun no benets to magnesium sulate tocolysis given to women with a preterm “nonsevere” abruption at 24 to 34 weeks’ gestation.
Cesarean Delivery
Te compromise etus is usually best serve by cesarean elivery, an the spee o response is an important actor in perinatal outcomes. In one stuy o 33 singleton pregnancies with a clinically overt placental abruption an etal braycaria, 15 o the 22 neurologically intact survivors were elivere within a 20-minute ecision-to-elivery interval (Kayani, 2003). However, eight o 11 inants who ie or evelope cerebral palsy were elivere ater a 20-minute intervals. Onishi an colleagues (2019) also oun a signicant negative correlation between these intervals an cor arterial pH. At Parklan Hospital, placental abruption was one o the most powerul anteceents to boy-cooling treatment or neonatal encephalopathy (Nelson, 2014).
A major hazar to cesarean elivery is impose by clinically signicant consumptive coagulopathy. Preparations inclue two large-bore intravenous catheters an plans or bloo an component replacement. Measures o hemoglobin, platelet, an brinogen levels as well as protime (P) an partial thromboplastin time (P) guie prouct replacement.
Vaginal Delivery
I the etus has ie, vaginal elivery is usually preerre. As reviewe earlier, hemostasis at the placental implantation site epens primarily on myometrial contraction an not bloo coagulability. Tus, ater vaginal elivery, uterotonic agents an uterine massage are use to stimulate myometrial contractions. Uterine muscle bers compress placental site vessels an prompt hemostasis even i coagulation is eective. In some instances, vaginal elivery may not be preerable, even with a ea etus. One example is brisk hemorrhage that cannot be successully manage by vigorous bloo replacement. Others are the myria obstetrical complications that prohibit vaginal elivery in general. In some women with extensive placental abruption, labor tens to be rapi because the uterus is usually persistently hypertonic (see Fig. 43-6). Tis can magniy etal compromise. In some cases, baseline intraamnionic pressures reach 50 mm Hg or higher, an with contractions, pressures may attain levels exceeing 100 mm Hg. Overall, however, rst- an secon-stage labor oes not appear to be shorter than usual (Downes, 2017).
Early amniotomy has long been champione in the management o placental abruption. Tis ostensibly achieves better spiral artery compression to iminish implantation site bleeing an reuce thromboplastin inusion into the maternal vascular system. Although evience supporting this theory is lacking, membrane rupture may hasten elivery. However, i the etus is small, the intact sac may be more efcient in promoting cervical ilation. I rhythmic uterine contractions are not superimpose on baseline hypertonus, oxytocin is given in stanar oses. No ata inicate that oxytocin augments thromboplastin escape into the maternal circulation to worsen coagulopathy. In 1ight o hypertonus associate with placental abruption, misoprostol may be a less avore inuction agent ue to its association with uterine tachysystole.
In the past, some ha set arbitrary time limits to permit vaginal elivery. Instea, experiences illustrate that maternal outcome epens on the iligence with which aequate ui an bloo replacement therapy are pursue rather than on the interval to elivery. Observations rom Parklan Hospital escribe by Pritchar an Brekken (1967) are similar to those rom the University o Virginia reporte by Brame an associates (1968). Specically, women with severe abruption who were transuse uring 18 hours or more beore elivery ha similar outcomes to those in whom elivery was accomplishe sooner.
Expectant Management
I possible, elaying elivery may benet an immature etus. In one series, 43 women with placental abruption beore 35 weeks’ gestation were expectantly manage, an 31 o them were given tocolytic therapy (Bon, 1989). Te mean interval until elivery or all 43 approximate 12 ays. Cesarean elivery was perorme in 75 percent, an there were no stillbirths. As iscusse earlier, women with a very early abruption may evelop chronic abruption–oligohydramnios sequence. In one report, our women with an abruption at a mean gestational age o 20 weeks subsequently evelope oligohyramnios an elivere at an average gestational age o 28 weeks (Elliott, 1998). In another escription o 256 women with an abruption at <28 weeks’ gestation, a mean o 1.6 weeks was gaine (Sabourin, 2012). O the group, 65 percent were elivere beore 29 weeks, an hal o all women unerwent emergent cesarean elivery.
Unortunately, even continuous etal heart rate monitoring oes not guarantee universally goo outcomes. A normal tracing may precee suen urther separation with instant etal compromise. In some o these, i the separation is sufcient, the etus will ie beore it can be elivere. ocolysis is avocate by some or suspecte abruption i the etus oes not isplay compromise. Some investigators have observe that tocolysis improve outcomes in a highly selecte cohort o women with preterm pregnancies (Bon, 1989; Combs, 1992). In another stuy, owers an coworkers (1999) aministere magnesium sulate, terbutaline, or both to 95 o 131 women with abruption iagnose beore 36 weeks’ gestation. Te perinatal mortality rate was 5 percent in both groups with or without tocolysis. Similar results were reporte rom a ranomize trial (Colón, 2016). A clinical consieration to the use o tocolytic agents, such as terbutaline, is that the rug-inuce tachycar- ia may mask maternal compromise. We are o the opinion that suspecte placental abruption contrainicates tocolytic agent use.
PLACENTA PREVIA
■ Classification
Te Latin previa means going before, an in this sense, the placenta goes beore the etus into the birth canal. Placenta previa escribes a placenta that is implante somewhere in the lower uterine segment, either over or very near the internal cervical os. Because these anatomical relationships cannot always be precisely ene an because they requently change across pregnancy, terminology can sometimes be conusing. erminology or placenta previa has evolve, an the National Institutes o Health (NIH)-sponsore Fetal Imaging Workshop (Rey, 2014) recommens the ollowing classication:
• Placenta previa: the internal os is covered partially or completely by placenta (Figs. 43-7 an 43-8). In the past, these were urther classie as either total or partial previa.
• Low-lying placenta: implantation in the lower uterine segment is such that the placental ege oes not cover the internal os but lies within a 2-cm wie perimeter aroun the os. A previously use term, marginal previa, escribe a placenta that was at the ege o the internal os but i not overlie it. Clearly, the classication o some cases will epen on cervical ilation at the time o assessment. For example, a low-lying placenta at 2-cm ilation may become a partial placenta previa at 4-cm ilation because the cervix has opene to expose the placental ege. Conversely, a placenta previa that appears to be total beore cervical ilation may become partial at 4-cm ilation because the cervical opening now extens beyon the ege o the placenta. Digital palpation in an attempt to ascertain these changing relations between the placental edge and internal os as the cervix dilates usually causes severe hemorrhage! With any egree o placenta previa, a certain amount o spontaneous placental separation is inevitable uring lower uterine segment remoeling an cervical ilation. Although this requently causes bleeing an thus technically constitutes a placental abruption, this term is usually not applie in these instances.
Somewhat but not always relate is vasa previa, in which etal vessels course through membranes an present at the cervical os. Vasa previa has been reviewe by the Society or Maternal–Fetal Meicine (2015) an is iscusse in Chapter 6 (p. 115).
■ Placental Migration
Beginning with the use o sonography in obstetrics, the term placental migration was coine to escribe the apparent movement o the placenta away rom the internal os (King, 1973). Obviously, the placenta oes not actually move, an the mechanism o apparent movement is not completely unerstoo. o begin with, migration is clearly a misnomer, because eciual invasion anchors chorionic villi.
Explanations o placental migration are likely aitive. First, apparent movement o the low-lying placenta relative to the internal os is relate to the imprecision o two-imensional sonography. Secon, as pregnancy progresses, growth o the lower an upper uterine segments iers. With greater bloo ow in the upper uterus, placental growth towar this supply, terme trophotropism, is thus more likely irecte towar the unus. Many o those placentas that “migrate” most likely never were circumerentially implante with true villous invasion that reache the internal cervical os. Importantly, a lowlying placenta or placenta previa is less likely to “migrate” if there is a prior cesarean delivery scar.
Te requency o placental migration has been quantie. In one stuy o 4300 women at mipregnancy, 12 percent ha a low-lying placenta (Sanerson, 1991). O placentas not covering the internal os, previa i not persist, an none subsequently ha placental hemorrhage. Conversely, approximately 40 percent o placentas that covere the os at mipregnancy continue to o so until elivery. Tus, placentas that lie close to but not over the internal os until the early thir trimester are unlikely to persist as a previa by term (Heller, 2014; Parrott, 2015). Te chance that placenta previa persists increases with a hysterotomy scar (Kohari, 2012; Oyelese, 2006).
■ Incidence and Associated Factors
Te incience o placenta previa has risen uring the past 30 years. Reporte inciences average about 0.4 percent or 1 case per 250 to 400 eliveries (Hill, 2020). Te requency at Parklan Hospital rom 1988 through 2003 or nearly 250,000 births was 2.6 cases per 1000. For the 2004 to 2020 epoch, it rose to 3.8 cases per 1000. Similar requencies have been reporte rom Austria, Finlan, an Israel (Kollmann, 2016; Räisänen, 2014; Rosenberg, 2011). Several emographic actors may contribute to this higher rate o placenta previa. First, maternal age increases the requency (Biro, 2012; Roberts, 2012). In the First- an Secon- rimester Evaluation o Risk (FASER) trial, which inclue more than 36,000 women, the requency o previa was 0.5 percent or women <35 years compare with 1.1 percent in those ≥35 years (Cleary–Golman, 2005). At Parklan Hospital, the incience range rom a rate o approximately 0.65 cases per 1000 births or women ≤19 years to almost 10 cases per 1000 births or women oler than 35.
Multiparity also elevates the rate o placenta previa (Räisänen, 2014). Obviously, the eects o avancing maternal age an parity are conouning. Still, Babinszki an colleagues (1999) reporte that the 2.2-percent incience in women with parity o ve or greater was signicantly higher than that o women with lower parity. Te interpregnancy interval oes not aect this rate (Fox, 2015).
Cigarette smoking increases the relative risk o placenta previa at least twool (Usta, 2005). It has been postulate that carbon monoxie hypoxemia causes compensatory placental hypertrophy an greater surace area. Smoking may also be relate to eciual vasculopathy.
Several clinical characteristics also raise placenta previa risks. Foremost, women with one or more prior cesarean deliveries are at greater risk or subsequent placental isorers that inclue placenta previa, placental abruption, or placenta accreta spectrum (PAS) (Gibbins, 2018; Klar, 2014). Te cumulative risks or placenta previa that accrue with the increasing number o cesarean eliveries are extraorinary. In one MFMU Network stuy o 30,132 women unergoing cesarean elivery, the inci- ence was 1.3 percent or those with only one prior cesarean elivery, but it was 3.4 percent i there were six or more prior cesareans (Silver, 2006). In a retrospective cohort o nearly 400,000 women who were elivere o two consecutive singletons, those with a cesarean elivery or the rst pregnancy ha a 1.6-ol greater rate or previa in the secon pregnancy (GurolUrganci, 2011). Tese same investigators reporte a 1.5-ol higher rate rom six similar population-base stuies. Tis risk is increase eightol in women with parity greater than our an who have more than our prior cesarean eliveries (Gilliam, 2002).
Importantly, women with a prior uterine incision an placenta previa have an increase likelihoo that cesarean hysterectomy will be necessary because o associate PAS (p. 761). In one stuy, 6 percent o women with a primary cesarean elivery or placenta previa require a hysterectomy. Tis rate was 25 percent or women with a placenta previa unergoing repeat cesarean elivery (Freeriksen, 1999).
Multifetal gestation raises placenta previa risk (Ananth, 2003a; Luke, 2017a). Compare with monochorionic twins, ichorionic ones show higher rates, which perhaps stems rom having two implantation sites (Weis, 2012). MSAFP levels, i abnormally elevate or otherwise unexplaine reasons uring prenatal screening, raise the risk or placenta previa an a host o other abnormalities. Moreover, women with a placenta previa an comorbi MSAFP level >2.0 multiples o the meian (MoM) at 16 weeks’ gestation were at greater risk or late-pregnancy bleeing an preterm birth (Chap. 17, p. 338).
Assisted reproductive technology (ART) use or conception elevates placenta previa rates. Some o this association may erive rom overlapping eects. First, oler women constitute a signicant portion o patients electing AR (Luke, 2017b). Secon, even ajusting or multietal gestation, AR is still associate with higher previa rates (Karami, 2018). Last, in one systematic review incluing nearly 256,000 births, uterine leiomyomas were associate with higher placenta previa rates (Jenabi, 2019).
■ Clinical Features
Painless bleeing is the most characteristic event with placenta previa. Bleeing usually oes not evelop until near the en o the secon trimester or later, but it can begin even beore mipregnancy. Unoubtely, some late abortions are cause by an abnormally locate placenta. Initial bleeing rom a previa usually begins without warning, an this sentinel bleed is rarely so prouse as to prove atal. Usually it ceases, only to recur.
However, in perhaps 10 percent o women, particularly those with a placenta implante near but not over the cervical os, bleeing is elaye until labor onset. Bleeing at this time varies in egree, an it may mimic placental abruption. In cases in which the placenta is locate over the internal os, a specic sequence o events leas to bleeing. First, the uterine boy remoels to orm the lower uterine segment. With this, the internal os ilates, an some o the implante placenta inevitably separates. Bleeing that ensues is augmente by the inherent inability o myometrial bers in the lower uterine segment to contract an thereby constrict torn vessels. Similarly, bleeing rom this lower-segment implantation site also requently continues ater placental elivery. Last, lacerations in the riable cervix an lower segment will blee. Tese may be especially problematic ollowing manual removal o a somewhat ahere placenta.
Cervical length may alter the clinical course. Staor (2010) but not ruell (2013), both with their associates, oun that a placenta previa an a thir-trimester cervical length <30 mm increase the risks or hemorrhage, uterine activity, an preterm birth. Similarly, Friszer (2013) but not ruell (2013), both with their coworkers, showe that women amitte or bleeing ha a greater chance o elivery in the subsequent 7 ays when the cervical length measure <25 mm sonographically.
Placenta accreta spectrum is a requent an serious complication associate with placenta previa. Tis abnormal placental attachment erives in part rom poorly evelope eciua that lines the lower uterine segment. Biswas an coworkers (1999) perorme placental be biopsies in 50 women with a placenta previa an in 50 control women. Inltration o spiral arterioles by trophoblastic giant cells, rather than by the expecte enovascular trophoblast cells, was oun in hal o specimens. In contrast, only 20 percent o biopsies rom normally implante placentas ha these changes. In another stuy o 514 cases o placenta previa, abnormal placental attachment was ientie in 7 percent (Freeriksen, 1999). As iscusse, placenta previa overlying a prior cesarean incision conveys a particularly high risk or PAS.
Coagulopathy rarely complicate placenta previa, even when implantation site separation is extensive (Cunningham, 2015). Placental thromboplastin, which incites the intravascular coagulation seen with placental abruption, is presume to reaily escape through the cervical canal rather than be orce into the maternal circulation. Te paucity o large myometrial veins in this area also may be protective.
■ Diagnosis
For uterine bleeing ater mipregnancy, placenta previa an placental abruption are always consiere. In one Canaian stuy, placenta previa accounte or 21 percent o women amitte rom 22 to 28 weeks’ gestation with vaginal bleeing (Sabourin, 2012). Previa shoul not be exclue until sonographic evaluation has clearly prove its absence. I sonography is not reaily available, iagnosis by igital cervical examination is one in an operating room an with preparations in place or operative elivery. We call these preparations a double setup technique. Even the gentlest examination can cause torrential hemorrhage.
Using stanar sonographic techniques, quick an accurate placental localization can be accomplishe (American Institute o Ultrasoun in Meicine, 2018). Tis is usually one with transabominal sonography. I the placenta clearly overlies the cervix or i it lies away rom the lower uterine segment, the examination has excellent sensitivity an negative preictive value (Olive, 2006; Quant, 2014). Obese women may hiner clear viewing o the lower uterine segment. A ull blaer may articially elongate the cervix an compress the lower uterine segment to give the impression that the placenta overlies the cervix.
I placental location remains unclear, transvaginal sonography is the most accurate sonographic metho an is sae even with vaginal bleeing (Fig. 43-9). In a comprehensive stuy, the internal os was visualize in all cases with transvaginal sonography but in only 30 percent with transabominal sonography (Farine, 1988). As iscusse, i the placental ege lies <2 cm rom the internal os, but not covering it, the placenta is consiere low lying (Rey, 2014). In the absence o any other inication, sonography nee not be requently repeate simply to ocument placental position. At Parklan Hospital, women with placenta previa ientie at 18 to 22 weeks’ gestation an a prior cesarean elivery are reevaluate sonographically at 28 weeks an again at 32 weeks i it persists. Tose with a placenta previa but without prior cesarean elivery unergo reimaging at 32 weeks. Restriction o activity is not necessary unless a previa persists beyon 28 weeks’ gestation or i clinical nings such as bleeing or contractions evelop beore this time. At 32 weeks’ gestation, i the placental ege is still <2 cm rom the os, transvaginal sonography is repeate at 36 weeks’ gestation. Using MR imaging, several investigators report excellent visualization o placental abnormalities. However, it is unlikely that this moality will replace sonography or routine evaluation anytime soon given availability an cost ierences compare with sonography. However, MR imaging is useul or evaluation o PAS (p. 761).
■ Management
Care with placenta previa is iniviualize, an three prominent actors inclue etal maturity, associate labor, an blee- ing severity. In one stuy o 214 women with a placenta previa, 43 percent ha an emergency elivery, an hal o these were preterm (Ruiter, 2015). Instea, i active bleeing subsies an the etus is immature, close observation in an obstetrical unit is inicate. Data are sparse regaring tocolytic aministration or uterine contractions. Although robust ranomize trials are lacking, Bose an colleagues (2011) recommen that i tocolytics are given, they be limite to 48 hours o aministration.
As note earlier, the physiological cariovascular responses to tocolytic agents that inclue hypotension an tachycaria can mask maternal compromise. We categorically recommen against their use in this setting. Ater bleeing has cease or approximately 2 ays an the etus is juge to be healthy, a woman can usually be ischarge home with instructions or “pelvic rest.” Te Society or Maternal–Fetal Meicine (2018) oes not recommen routine cervical length screening in these women. Importantly, the woman an her amily must appreciate the possibility o recurrent bleeing an be prepare or immeiate transport back to the hospital. In other cases, prolonge hospitalization may be necessary.
Te requency o emergency elivery in women with placenta previa ranges rom 25 to 40 percent (Erani, 2019; Gibbons, 2018). In properly selecte patients, however, long-term inpatient care oes not appear to a benets compare with outpatient management (Neilson, 2003). In one ranomize stuy o 53 women who ha a bleeing previa at 24 to 36 weeks’ gestation, maternal or etal morbiity rates i not ier between management methos (Wing, 1996). O all stuy women, 60 percent ha recurrent bleeing, an hal eventually require expeitious cesarean elivery.
For women who are near term an who are not bleeing, plans are mae or scheule cesarean elivery. A planne elivery in a controlle setting is optimal, an timing balances etal immaturity against antepartum hemorrhage. Te American College o Obstetricians an Gynecologists an Society or Maternal–Fetal Meicine (2021) recommen elivery or otherwise uncomplicate placenta previa between 360/7 an 376/7 weeks. At Parklan Hospital, we usually perorm elective cesarean elivery at 380/7 weeks. Recommenations or elivery o women with PAS are outline in that section.
■ Delivery
Practically all women with placenta previa unergo cesarean elivery. Some recommen a vertical laparotomy incision to provie rapi entry i bleeing is torrential or i generous operating space is require or hysterectomy. As iscusse, cesarean elivery is emergently perorme in more than hal because o hemorrhage, or which about a ourth require bloo transusion (Sabourin, 2012). Although a low transverse hysterotomy is usually possible, this may cause etal bleeing i the placenta is implante anteriorly an the placenta is incise. In such cases, etal elivery shoul be expeitious (Silver, 2015a). Tus, a vertical uterine incision may be preerable in some instances.
In either case, even when the incision extens through the placenta, maternal or etal outcomes are rarely compromise. Following placental removal, the implantation site may blee uncontrollably ue to poorly contracte smooth muscle, which is characteristic o the lower uterine segment. I hemostasis at the placental implantation site cannot be obtaine by uterotonic agent aministration an pressure, it can be oversewn with no. 0 chromic sutures. Cho an associates (1991)
escribe placing interrupte sutures at 1-cm intervals to orm a circle aroun the bleeing portion o the lower segment to control hemorrhage. Others have reporte success with compression sutures that traverse an compress the anterior an posterior uterine wall (Mohame, 2019; Sallam, 2019). O other methos, Bakri or Foley balloon tamponae use alone or couple with compression sutures has been escribe (Albayrak, 2011; Diemert, 2012). Other surgical options are bilateral uterine or internal iliac artery ligation, illustrate in Chapter 44 (p. 779). Pelvic artery embolization also has gaine acceptance. Yu an colleagues (2020) perorme a ranomize trial o perioperative prophylactic internal iliac artery balloon occlusion uring cesarean elivery or placenta previa an oun that eployment i not reuce postpartum hemorrhage or alter maternal or neonatal morbiity.
I these more conservative methos ail an bleeing is brisk, hysterectomy is necessary. Placenta previa—especially with PAS—currently is a common inication or peripartum hysterectomy at Parklan Hospital an other institutions (Jakobsson, 2015; Wong, 2011). In cases without PAS, the reporte incience o hysterectomy with placenta previa is 2 percent (Gibbins, 2018).
Tus, it is not possible to accurately estimate the eect on the hysterectomy rate rom placenta previa alone without consiering the associate PAS. Again, for women whose placenta previa is implanted anteriorly at the site of a prior uterine incision, the likelihood of an associated morbidly adherent placenta and need for hysterectomy is increased. In a stuy o 318 peripartum hysterectomies perorme in the Unite Kingom, 40 percent were one or abnormal placentation (Knight, 2007). At Parklan Hospital, 44 percent o cesarean hysterectomies were one or bleeing placenta previa or or PAS (Wortman, 2015). Te technique or peripartum hysterectomy is escribe in Chapter 30 (p. 560).
■ Maternal and Perinatal Outcomes
Placenta previa an coexistent PAS both contribute substantively to maternal morbiity an mortality rates. Te maternal mortality ratio is increase approximately threeol or women with a placenta previa (Gibbins, 2018). In a report o 5367 maternal eaths in the Unite States rom 2006 to 2013, placenta previa alone accounte or nearly 3 percent o eaths rom hemorrhage (Creanga, 2014, 2017).
Te report rom the Consortium on Sae Labor emphasizes the ongoing perinatal morbiity with placenta previa (Lai, 2012). In these cases, preterm elivery continues to be a major cause o perinatal eath (Balachanar, 2020; Nørgaar, 2012; Salihu, 2003). Ananth an colleagues (2003b) reporte a comparably elevate risk o neonatal eath even or etuses who elivere at term. Tis is at least partially relate to the etal anomaly rate, which is two- to threeol higher in pregnancies with placenta previa (Crane, 1999; Kancherla, 2015).
Te association o etal-growth restriction with placenta previa is likely minimal ater controlling or gestational age. In a population-base cohort o more than 500,000 singleton births, most low-birthweight newborns associate with placenta previa resulte rom preterm birth (Ananth, 2001). From their large metaanalysis, Balayla an coworkers (2019) oun a slightly increase requency o etal-growth restriction. At least two other stuies reporte an elevate risk (Räisänen, 2014; Weiner, 2016). Apparently, etal growth eects are similar with placenta previa an PAS (Jauniaux, 2019).
PLACENTA ACCRETA SPECTRUM
Te term placenta accreta spectrum (PAS) escribes aberrant placentation characterize by abnormally implante, invasive, or ahere placenta. Derivation o accreta comes rom the Latin ac- + crescere—to ahere or become attache to (Benirschke, 2012). It is also reerre to as the morbily aherent placenta, an in Europe it is reerre to as a pernicious placenta previa with accreta an abnormally adherent placenta.
■ Etiopathogenesis
Te major clinical problem is placental ailure to separate normally rom the myometrium ater etal elivery. Tis abnormal aherence stems in part rom partial or total absence o the eciua basalis an imperect evelopment o the brinoi or Nitabuch layer, escribe in Chapter 5 (p. 85). I the eciual spongy layer is lacking either partially or totally, the physiological line o cleavage is absent, an some or all cotyleons are ensely anchore. Microscopically, placental villi attach to smooth muscle bers rather than to eciual cells. Tis eci- ual eciency then prevents normal separation ater elivery.
Te surace area involve at the implantation site an the epth o trophoblast ingrowth vary between women, but all aecte placentas can potentially cause signicant hemorrhage. Data now suggest that PAS is not solely cause by the eci- ua’s anatomical eciency. Inee, the cytotrophoblasts may control eciual invasion through actors such as angiogenesis (Duzyj, 2018; Goh, 2016). Moreover, some tissue specimens show immunologically meiate “hyperinvasiveness” (Harris, 2019). Some genes that coe or remoeling an or aherence may be highly expresse (Matsukawa, 2019; Shainker, 2020).
Myometrial bers attache to the basal plate in an anteceent pregnancy are preictive markers or a subsequent PAS (Linn, 2015; Miller, 2016). Tis implies an anteceent "constitutional enometrial eect” in most cases. Te greater risk conveye by previous surgical uterine trauma may be partially explaine by an enhance vulnerability to trophoblast invasion (Einerson, 2020; Jauniaux, 2018).
Tis association with prior trauma is reinorce by the close relationship between cesarean scar pregnancy (CSP) an later evelopment o PAS in the same pregnancy. Inee, accruing evience suggests that CSP an PAS lie on a spectrum an that CSP is a precursor (Happe, 2020; imor-ritsch, 2019). Describe in Chapter 12 (p. 229), early rupture an hemorrhage with CSP are not uncommon, an women oten elect pregnancy-terminating interventions to avoi these (Society or Maternal–Fetal Meicine, 2020; imor-ritsch, 2019).
■ Classification
Variants o PAS are classie by the epth o trophoblastic growth (Figs. 43-10 an 43-11). Placenta accreta inicates that villi are attache to the myometrium. With placenta increta, villi actually invae the myometrium, an placenta percreta enes villi that penetrate through the myometrium an to or through the serosa (Silver, 2018). In clinical practice, these three variants are encountere in an approximate ratio o 80:15:5, respectively (Wong, 2008). At a reerral center, however, the istribution was 22, 24, an 54 percent respectively (Birgani, 2020). In all three varieties, abnormal aherence may involve all lobules—total placenta accreta. I all or part o a single lobule is abnormally attache, it is escribe as focal placenta accreta.
Histological iagnosis cannot be mae rom the placenta alone, an myometrial samples are necessary or conrmation (Jauniaux, 2021). erminology or consistent classication has been lacking because o varying clinical criteria an lack o etaile pathological examinations. o alleviate this, the International Feeration o Gynecology an Obstetrics (FIGO) has recently propose a clinical classication system or PAS (Jauniaux, 2019).
■ Incidence and Risk Factors
Decaes ago, the requency o PAS was 1 in 20,000 births (McKeogh, 1951). As late as 1971, Hellman an Pritchar in the 14th eition o Williams Obstetrics escribe PAS as the subject o case reports. Since then, the incience has grown remarkably in irect relationship to the rising cesarean elivery rate. For example, the incience was 1 case in 2500 births in the 1980s, but it was 1 case per 731 births in a report rom the MFMU Network comprising 115,502 women (Bailit, 2015). From the Nationwie Inpatient Sample, the PAS rate was an astouning 1 case in 270 births (Mogos, 2016).
Tis rising requency has mae PAS one o the most ormiable problems in obstetrics. O 5367 pregnancy-relate maternal eaths in the Unite States rom 2006 to 2013, 13 percent were ue to hemorrhage cause by PAS (Creanga, 2015, 2017). In aition, PAS is a leaing cause o hemorrhage an emergency peripartum hysterectomy (Awan, 2011; Eller, 2011; Rossi, 2010). Te American College o Obstetricians an Gynecologists an the Society or Maternal–Fetal Meicine (2018) have outline optimal management. Te International Society or Abnormally Invasive Placenta also has publishe guielines (Collins, 2019).
In subsequent pregnancies ollowing PAS, recurrence risks are high. Women in whom hysterectomy is avoie have an estimate 20-percent incience o recurrence (Cunningham, 2016; Roeca, 2017). Some evience shows that these women also have greater risks or placenta previa, uterine rupture, manual placental removal, preterm elivery, an hysterectomy (Balwin, 2020; Eshkoli, 2013). PAS risk actors are similar to those or placenta previa (p. 756). Shown in Figure 43-12, the two most important elements are an associate placenta previa, a prior cesarean elivery, or more likely both (Klar, 2014; Silver, 2006). A classical hysterotomy incision has a higher risk or subsequent PAS than a lower uterine segment one (Gyam-Bannerman, 2012). O women with a prior cesarean elivery, almost hal ha myometrial bers seen microscopically ahere to the placenta (Hararottir, 1996; Miller, 2016). Dysunctional eciua may also ollow other myometrial trauma such as curettage or enometrial ablation (Balwin, 2018; Gill, 2015). AR is an inepenent risk actor or PAS (Salmanian, 2020).
Other risk markers are prenatal MSAFP an human chorionic gonaotropin (hCG) use to screen or neural-tube eects an aneuploiies. In one stuy o more than 9300 women screene at 14 to 22 weeks’ gestation, the risk or PAS was eightol higher with MSAFP levels >2.5 MoM, an it was increase ourol with maternal serum ree β-hCG levels >2.5 MoM (Hung, 1999).
■ Diagnosis
With rst- an secon-trimester PAS, hemorrhage usually stems rom a coexisting placenta previa. Such bleeing will typically prompt evaluation, an ieally sonography is use (Chantraine, 2013; Jauniaux, 2018). With lesser egrees o bleeing, rst-trimester measurement o the smallest myometrial thickness can help preict the later risk or peripartum hysterectomy with PAS (Happe, 2020). In a screening stuy o more than 22,000 singleton pregnancies at 11 to 13 weeks’ gestation, 6 percent were at high risk or PAS (Panaiotova, 2019). However imaging was less than perect to ientiy all o these placentas early. Subsequently, only 14 ha a suspecte clinical iagnosis, an 13 o these were conrme at elivery.
Five characteristic sonographic nings suggest PAS: (1) placental lacunae; (2) thinning o the retroplacental myometrium; (3) isruption o the blaer-uterine serosal interace; (4) briging vessels rom the placenta to the blaer-serosal interace; an (5) placental bulge that pushes outwar an istorts the contour o the uterus (Fig. 43-13). In a metaanalysis, the sensitivities o these criteria to ientiy placenta accreta, increta, an percreta were 91, 93, an 89 percent, respectively. Corresponing specicities were 97, 98, an 99 percent, respectively (Pagani, 2018).
Tese gures may be overestimate because o clinical bias an consierable interobserver variability (Silver, 2018). Some investigators report ewer spectacular results with sonography (Jauniaux, 2016; Primo, 2014). Bowman an colleagues (2014) escribe the sensitivity o sonography to be 54 percent; speci- city, 88 percent; positive preictive value, 82 percent; negative preictive value, 65 percent; an accuracy, 65 percent. Location aects sonographic accuracy. Posterior placental location is associate with elaye iagnosis an increase surgical complications (Morgan, 2019; inari, 2021). In one stuy, the etection rate was 90 percent or anterior placenta accreta compare with 50 percent or posterior ones (Pilloni, 2016). Nageotte (2014) conclue that ientication o PAS with sonography shoul be interprete with clinical an operative nings.
Better results have been oun by some using three-imensional (3-D) sonography an power Doppler (Collins, 2015). We too have oun that the aition o Doppler color ow mapping ais preiction o myometrial invasion (Fig. 43-14). Invasion is suspecte i the istance between the uterine serosa– blaer wall interace an the retroplacental vessels measures <1 mm an i large intraplacental lacunae are seen (Rac, 2015a; wickler, 2000). In another stuy, hypervascularity o the uterine serosa–blaer wall interace ha the highest positive an negative preictive values or placenta percreta (Cali, 2013). Intracervical lakes also have been reporte with placenta percreta (i Pasquo, 2020). Yule an coworkers (2020) reporte that the placenta accreta index was useul or iagnosis. Tis inex incorporates the number o prior cesarean eliveries, placental location, lacunae, briging vessels, an smallest myometrial istance. Tese investigators are also exploring rst-trimester color mapping to evelop a quantication algorithm (Yule 2021). o urther elineate anatomy, MR imaging can be ae.
We an others use it to ientiy invasion o ajacent structures (Chalubinski, 2013; Rey, 2014). Interobserver variability was reporte to be excellent to iagnose PAS an assess invasion epth. Tere was less agreement in assessing topography o invasion (Finazzo, 2020). Using MR imaging, Mori an colleagues (2020) escribe a high prevalence o pelvic parasitic arteries with PAS. However, not all investigators have oun MR imaging to be benecial (Einerson, 2018). Although gaolinium is usually not ae uring pregnancy, this contrast may enhance images (Millischer, 2017). Lax an coworkers (2007) escribe three MR imaging n- ings that suggest PAS: uterine bulging, ark intraplacental bans on 2-weighte imaging, an heterogeneous signal intensity within the placenta inicative o lacunae. Some recommen MR imaging i sonography results are inconclusive or there is a posterior previa (American College o Obstetricians an Gynecologists, 2018; Silver, 2018).
■ Management
Preoperative assessment ieally begins once a possible PAS is recognize antenatally. A major decision concerns the timing and the ideal facility for delivery. Consierations inclue appropriate surgical, anesthesia, intensive care, an bloo banking capabilities. An obstetrical surgeon or gynecological oncologist an surgical, urological, an interventional raiological consultants shoul be available (Collins, 2019; Shamshirsaz, 2018). Te American College o Obstetricians an Gynecologists (2018) an the Society or Maternal–Fetal Meicine recommen planne elivery in a tertiary-care acility. In some, specially esigne teams have been assemble an are on call (Shamshirsaz, 2018). A metaanalysis escribe the improve maternal outcomes with such management (Bartels, 2018). Silver an colleagues (2015b) have provie requisites or accreta centers o excellence an their criteria to consier trans- er to a higher level-o-care hospital (Table 43-2). I possible, elivery is best scheule or peak availability o all resources an team members. Even so, a thir o cases require unsche- ule elivery, an contingency plans shoul be reay (Pettit, 2019). Women who reuse bloo or its erivatives pose especially ifcult management ilemmas (Barth, 2011).
Delivery Timing
In one stuy, 40 percent o women with PAS ha bleeing manating unplanne elivery prior to 34 weeks’ gestation. iming balances etal immaturity against averse maternal consequences o hemorrhage an emergency cesarean elivery (Perlman, 2017; Pettit, 2019). Te American College o Obstetricians an Gynecologists (2018; 2021) recommens iniviualization an suggests elivery between 340/7 an 356/7 weeks’ gestation. Tey cite a ecision-analysis stuy that justi- es elective elivery without etal lung maturity testing ater 34 complete weeks (Robinson, 2010). Te Society or Maternal– Fetal Meicine (2018) recommens elivery between 34 an 37 weeks. wo earlier surveys oun that most practitioners o not eliver these women until 36 weeks or later (Esako, 2012; Wright, 2013). At Parklan Hospital, we generally scheule these proceures ater 36 complete weeks but are prepare also to manage them in nonelective situations (Rac, 2015b). In some cases, PAS is not recognize until laparotomy. I resources are inaequate to surgically manage the percreta an i the woman is stable an not bleeing, the etus is not elivere. Te abominal incision is close, an she is transerre to a tertiary-care acility.
Preoperative Prophylactic Catheterization
In cases that may involve the ureters, catheterization may ai their issection or ientication. However, these catheters overall o not lower urinary tract injury rates (Crocetto, 2021). Some, but not all, avocate preoperative ureteral catheterization (American College o Obstetricians an Gynecologists, 2018; Eller, 2011). Te role o catheters or ureteral injury repair is outline in Chapter 30 (p. 564). With arterial catheterization, balloon-tippe catheters aim to mitigate bloo loss an thereby enhance surgical visibility. Catheters are avance preoperatively into the internal iliac arteries an are inate ater etal elivery to occlue pelvic bloo ow (Ballas, 2012; Desai, 2012; Zhou, 2021). Some pre- er an inrarenal aortic balloon occlusion catheter (Mei, 2020). Alternatively, the catheters can be use to eliver occluing emboli to bleeing arterial sites (Mei, 2018). Others have conclue that these proceures oer borerline efcacy an have serious risks (Chen, 2020; Makary, 2019; Mohr-Sasson, 2020). Rare complications have inclue thrombosis o the common iliac artery (Bishop, 2011). At this time, the American College o Obstetricians an Gynecologists (2018) conclues that a rm recommenation cannot be mae or or against intraarterial catheter use. Similarly, there are no obvious benets to prophylactic internal iliac artery ligation in this setting (Po, 2012; Yu, 2020).
Cesarean Delivery and Hysterectomy
Beore commencing with elivery, the risk o hysterectomy to prevent exsanguination shoul be estimate. Some o these abnormal placentations, especially i partial, may be amenable to placental elivery with hemostatic suture placement. Con- rmation o a percreta or increta almost always manates hysterectomy. Because the scope o invasion may not be apparent beore elivery o the etus, some complete a number o issection steps early. Tis also minimizes bloo loss uring potentially teious issection ater hysterotomy an i the placenta blees. Tus, an attempt can be mae to create a wie blaer ap beore making the hysterotomy incision (Cunningham, 2017). Te roun ligaments are ivie, an the lateral eges o the peritoneal reection are issecte ownwar. I possible, these incisions are extene to encircle the entire placental implantation site that visibly occupies the prevesical space an posterior blaer wall. Following this, a classical hysterotomy, transverse unal, or high posterior incision is mae to avoi the placenta (Kotsuji, 2013).
After fetal delivery, the extent of placental invasion is assessed without attempts at manual placental removal. In a report rom the Unite Kingom, attempts at partial or total placental removal prior to hysterectomy were associate with twice as much bloo loss (Fitzpatrick, 2014). Generally speaking, with obvious percreta or increta, hysterectomy is usually the best course, an the placenta is let in situ. With more extensive placental ingrowth, bleeing may be minimal until manual placental removal is attempte. Unless there is spontaneous separation with bleeing that manates emergency hysterectomy, the operation begins ater ull assessment is mae. Cesarean hysterectomy is carrie out as escribe in Chapter 30 (p.560). With heavy bleeing, successul treatment epens on imme- iate bloo replacement an other measures that can inclue uterine or internal iliac artery ligation, balloon occlusion, or embolization. In some cases, the operation is mae easier by perormance o a supracervical hysterectomy (Levin, 2020). Kingom an colleagues (2020) have escribe a moie raical hysterectomy or PAS (Table 43-3). Tis technique is also etaile in Cunningham and Gilstrap’s Operative Obstetrics, 3r eition (Cunningham, 2017). Because o a high risk or postoperative venous thromboembolism, consieration is given or thromboprophylaxis (Silver, 2018).
Conservative Management
Occasionally, it may be possible to trim the umbilical cor, repair the hysterotomy incision, leave the placenta in situ, an not pursue hysterectomy (Sentilhes, 2021). Tis option may be use or women in whom abnormal placentation was not suspecte beore cesarean elivery an in whom uterine closure stops bleeing. Ater this, she can be transerre to a higher level-o-care acility or enitive management. Another consieration is the woman with a strong esire or ertility an who has receive extensive counseling. Resection o the aherent placenta an unerlying myometrium has been avocate as a uterine-sparing technique (Palacios-Jaraquemaa, 2020). Conservative management was reviewe by Perez-Delboy (2014) an Fox (2015) an their colleagues. In some o these cases, the placenta spontaneously resorbe between 1 an 12 months with a mean o 6 months. Numerous complications can occur an inclue sepsis, coagulopathy, pulmonary embolism, an arteriovenous malormation (Fox, 2015; Juy, 2015; Roach, 2015).
In other cases, sutures are place through the outsie wall o the uterus overlying the placental be. Shih an associates (2019) escribe this using a Nausicaa proceure. In some o these women, a subsequent hysterectomy— either planne or prompte by bleeing or inection—is per- orme ays to weeks postpartum when bloo loss might be less (Al-Khan, 2014; Sentilhes, 2009, 2021; Zuckerwise, 2020). In some stuies, 20 percent or ewer o women ultimately require hysterectomy (Bretelle, 2007; Kutuk, 2018). In other reports, however, up to 60 percent eventually require emergency hysterectomy (Clausen, 2013; Pather, 2014). Evience that treatment with methotrexate ais resorption is lacking. Last, or women in whom the placenta is let in situ, serial serum β-hCG measurements are not inormative, an serial sonographic or MR imaging is recommene (immermans, 2007; Worley, 2008).
At this time, we agree with the American College o Obstetricians an Gynecologists (2018) that leaving the placenta in situ shoul be consiere investigational. Exceptions permit transer to a higher level o care. Guielines rom the International Society or Abnormally Invasive Placenta are more permissive (Collins, 2019).
■ Pregnancy Outcomes
In sum, PAS can have isastrous outcomes or both mother an etus. Although the epth o placental invasion oes not correspon with perinatal outcome, it is o paramount maternal signicance. Table 43-4 isplays outcomes o women at tertiary-care hospitals an in whom the PAS iagnosis was usually mae preoperatively. Despite these avantages, complications inclue hemorrhage, urinary tract injury, intensive care unit amission, seconary surgical proceures, an maternal eath. Some o these same reports chronicle outcomes in a secon cohort o women in whom care was not given at a tertiary-care acility or in whom the iagnosis o percreta was not mae until elivery, or both. In these cohorts, morbiity an mortality rates were higher (Erani, 2019)
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