Case 28. Prenatal Care

 A 35-year-old G2P1001 woman is seen for her first prenatal visit. Based on her last

menstrual period, she is at 15 weeks’ gestation. She has no complaints and has

no significant medical history. She denies dysuria or urinary urgency. Her surgical

history is remarkable only for “ear tubes” as a child. Her last delivery was a vaginal delivery and was uncomplicated. She has had Pap smears each year which to

her memory “have been normal.” On examination, she is a well-appearing white

female in no distress. Her blood pressure is 100/65 mm Hg, heart rate is 90 beats

per minute (bpm), respiratory rate is 12 breaths per minute, temperature is 98°F

(36.6°C), and weight is 130 lb. Her general physical examination is normal. The

breasts are nontender and without masses or skin changes. The heart reveals

II/VI systolic ejection murmur. The lungs are clear. Her abdomen is nontender and

her fundal height is at the level of the umbilicus. Fetal heart tones are 140 bpm.

The pelvic examination reveals a normal external genitalia, normal-appearing

vagina and cervix. The bimanual examination shows adequate pelvimetry, and

nontender uterus without adnexal or other masses. The cervix is normal in consistency and without masses. Her extremities are without edema. Prenatal laboratories are obtained and reveal the following:

CBC: Hgb 10.0 g/dL, MCV 82 fLPlt, 150 000/mm3, WBC 8000/mm3

Rubella: nonimmune Hepatitis B surface antigen: positive

Blood type: O, Rh-negative Indirect Coombs (antibody screen): negative

HIV ELISA: negative UC&S: 10 000 cfu/mL of group B streptococcus

RPR: negative Pap smear: ASC-US

Gonorrhea assay: negative Chlamydia assay: negative

» What items should be listed on the problem list?

» What is your next step for the problems listed?

» What other testing should be recommended to the patient?

CASE 28

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ANSWERS TO CASE 28:

Prenatal Care

Summary: A 35-year-old G2P1001 white female at 15 weeks’ gestation whose prior

delivery was normal. H er fundal height is at the umbilicus. Fetal heart tones are

140 bpm. Prenatal laboratory results indicate a hemoglobin level of 10.0 g/ dL with

MCV 82 fL; hepatitis surface antigen positive; Rh-negative blood type, negative

indirect Coombs; urine culture revealing 10 000 cfu/ mL of group B streptococcus;

and a Pap smear showing ASC-US.

 Problem list:

1. Advanced maternal age (AMA)—age 35 or greater at estimated time of

delivery.

2. Size greater than dates (fundal height at umbilicus corresponds to 20 weeks).

3. Mild microcytic anemia (H gb < 10.5).

4. Hepatitis B surface antigen (H BsAg) positive.

5. Rh-negative blood type with negative indirect Coombs.

6. Urine culture with GBS 10 000 cfu/ mL, asymptomatic.

7. Pap smear showing atypical squamous cells of undetermined significance

(ASC-US).

8. Rubella nonimmune.

 Next steps:

1. AMA—genetic counseling and discuss invasive testing (amniocentesis)

versus noninvasive prenatal testing.

2. Size/ dates—fetal ultrasound to assess gestational age, multiple gestation,

or cell-free fetal DNA testing (see Case 7).

3. Anemia—therapeutic trial of iron.

4. H BsAg positive—check liver function tests and hepatitis B serology to

assess for active hepatitis versus chronic carrier status.

5. Rh-negative with indirect Coombs negative—RhoGAM at 28 weeks and at

delivery if the baby proves to be Rh-positive.

6. Urine culture with GBS—treat with ampicillin and reculture urine, penicillin IV prophylaxis in labor.

7. Pap smear ASC-US—observe and repeat Pap smear postpartum.

8. Rubella status—vaccinate postpartum.

 Other testing: Cystic fibrosis screening; consider early diabetic screen.

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ANALYSIS

Objectives

1. Describe the routine prenatal care and the key screening strategies.

2. Be able to understand the principle of developing a problem list and its importance.

3. Be able to describe the “next steps” with any abnormal finding and know its

significance.

Considerations

This is a 35-year-old woman who is seen for her first prenatal visit. Since pregnancy

and delivery is a normal physiological process, the purpose of the prenatal care is

to educate and build rapport with the patient and family, establish gestational age,

screen for possible conditions that may impact maternal or fetal health, and monitor the progress of the pregnancy. During the first visit, a fairly extensive process

is used to screen for at-risk conditions using a detailed history, general physical

examination, and laboratory panel. This patient has a variety of conditions that

need addressing. The best way to ensure that each issue is dealt with in a systematic

manner and until resolution is to use a “problem list.” Thus, numerous issues are

written into the problem list, and investigation is performed until resolution of the

problem. An understanding of the strategy and approach to addressing each issue is

fundamental to the care of patients. Likewise, an understanding of the physiologic

changes of pregnancy allows for interpretation of physical examination findings

and impact of various diseases (see Table 28– 1).

Table 28–1 • PHYSIOLOGICAL CHANGES IN PREGNANCY

Parameter Comment

Cardiovascular Cardiac output

and plasma

volume

increased 50%

Systemic

vascular resistance decreased

Mean arterial

pressure

unchanged/

slightly lower

Pregnancy increases

intravascular volume

Respiratory Respiratory rate

unchanged

Tidal volume

increased

Minute ventilation increased

Ventilation exceeds

needs

Arterial

blood gas

pH 7.45

(increased)

PCO

2 28

(decreased)

HCO

3 18

(decreased)

Primary respiratory

alkalosis and

partial metabolic

compensation

Renal GFR—increased

50%

Serum Cr

decreased

Ureteral caliper

dilated

GFR increased and

creatinine clearance

also increased

Hematologic Hemoglobin

decreased

slightly

Platelet

decreased

slightly

Leukocyte

count slightly

increased

Physiologic anemia

due to plasmavolume

increased more than

red blood cell mass

Gastrointestinal Delayed stomach emptying

Decreased lower

esophageal

sphincter tone

Decreased gut

motility

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For instance, this 35-year-old patient has an early systolic ejection murmur, very

common in pregnancy due to the increased cardiac output. A diastolic murmur,

however, would be abnormal. Although the American College of Obstetricians

and Gynecologists recommends counseling to every pregnant patient about cystic

fibrosis screening; Caucasian patients are at particular risk with gene frequency

being about 1 in 40. Also for women over the age of 30, some practitioners will perform a glucose screen for gestational diabetes early (eg, 18 weeks), and if negative,

then again at the time of universal screening, 26 to 28 weeks’ gestation.

APPROACH TO:

Prenatal Care

DEFINITIONS

ADVANCED MATERNAL AGE:Pregnant woman who will be 35 years or beyond

at the estimated date of delivery.

ISOIMMUNIZATION:The development of specific antibodies as a result of antigenic stimulation by material from the red blood cells of another individual. For

example, Rh isoimmunization means an Rh-negative woman who develops anti-D

(Rh factor) antibodies in response to exposure to Rh (D) antigen.

ASYMPTOMATIC BACTERIURIA: Urine culture of 100 000 cfu/ mL or more of

a pure pathogen of a midstream-voided specimen.

GENETIC COUNSELING:An educational process provided by a health-care professional for individuals and families who have a genetic disease or who are at risk

for such a disease. It is designed to provide patients and their families with information about their condition or potential condition and help them make informed

decisions.

VERTICAL TRANSMISSION: The passage of infection from mother to fetus,

whether in utero, during labor and delivery, or postpartum.

ANTENATAL TESTING: A procedure that attempts to identify whether the

fetus is at risk for uteroplacental insufficiency and perinatal death. Some of these

tests include nonstress test and biophysical profile.

BASIC OBSTETRICAL ULTRASOUND: Sonographic examination focused on

fetal biometry (dating and fetal weight), number of fetuses, fetal presentation, placental location, amniotic fluid volume, and limited fetal anatomical survey.

COMPREHENSIVE (OR TARGETED) ULTRASOUND: Detailed anatomical

evaluation to assess a suspected structural anomaly.

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CLINICAL APPROACH

Physiological Changes

Pregnancy is associated with numerous physiological changes. An understanding

of these changes is critical in the interpretation of laboratory tests, or a rational

awareness of how disease processes may impact the pregnant patient. Some “seemingly abnormal” findings will be normal in pregnancy such as glycosuria due to the

increased glomerular filtration rate delivering more glucose to the kidneys. Other

findings in pregnancy will appear to be normal, but are “worrisome” in pregnancy;

for instance, when the PCO 2 level is 40 mm H g (normal for nonpregnant), it indicates significant CO 2 retention and possibly impending respiratory failure.

Dating

The priorities of prenatal care includes establishment of gestational age since

all of the monitoring, assessments, and milestones are based on gestational age.

H istory of the LMP, regularity of menses, medication use that may affect ovulation, physical examination, and early ultrasound help this determination. On

examination, the fundal height in centimeters corresponds to the gestational age

from 20 to 34 weeks. An ultrasound will be obtained when there is a discrepancy

of 3 cm or more.

Prevention

Much of prenatal care involves educating the patient, screening for diseases or

unsafe conditions (intimate partner violence), and preventive measures. Use of

immunizations (influenza and RhoGAM), prenatal vitamin with folate, iron supplementation, and a balanced diet are recommended.

Screening for Conditions of Risk

Much of the time spent in caring for the pregnant patient is involved in trying

to identify high-risk conditions and taking the proper steps to reduce the risk, or

minimize complications (see Table 28– 2).

Because both maternal and fetal health are being considered, any high-risk condition must be balanced from both perspectives. Many of the cases involve antepartum, intrapartum, or postpartum complications (see Table 28– 3).

www.myuptodate.comTable 28–2 • SUMMARY OF PRENATAL LABORATORIES, RAMIFICATIONS, AND EVALUATION

Lab Test Finding Ramifications Next Step Comments

Hemoglobin <10.5 g/dL Preterm delivery, low fetal iron

stores, identify thalassemia

Mild therapeutic trial of iron, moderate

ferritin and Hb electrophoresis

Rubella Negative Nonimmune to rubella Stay away from sick individuals, vaccinate

postpartum

Live-attenuated vaccine

Blood type Any type May help pediatricians identify

ABO incompatibility

Rh factor Negative May be susceptible to Rh disease If antibody screen negative, give RhoGAM

at 28 wk, and if baby is Rh-positive, then

also after delivery

Antibody screen Positive May indicate isoimmunization Need to identify the antibody, and then

titer

Lewis lives, Kell kills, Duffy dies

HIV ELISA (or Fourth

Generation Ag/Ab test)

Positive May indicate infection with HIV Western blot or PCR, if positive then place

patient on anti-HIV medicines, offer elective cesarean, or IV ZDV in labor

Intervention reduces vertical transmission from 25% to 2%

RPR or VDRL Positive May indicate syphilis Specific antibody such as MHA-TP, and if

positive, then stage disease

Less than 1 yr, penicillin × 1; >1 year

or unknown, penicillin IM each

week × 3

Gonorrhea Positive May cause preterm labor, blindness

Ceftriaxone IM

Chlamydia Positive May cause neonatal blindness,

pneumonia

Azithromycin or amoxicillin orally

Hepatitis B surface

antigen

Positive Patient is infectious Check LFTs and hepatitis serology to

determine if chronic carrier vs active

hepatitis

Baby needs HBIG and hepatitis B

vaccine

www.myuptodate.comUrine culture Positive Asymptomatic bacteriuria may

lead to pyelonephritis 25%

Treat with antibiotic and recheck urine

culture

If GBS is organism, then give penicillin in labor

Pap smear Positive Only invasive cancer would alter

management

ASC-US = re-Pap postpartum; LGSIL,

HSIL = colposcopy

Reflexive HPV not recommended

with ASC-US

Nuchaltranslucency

(11-13 wk)

Positive May indicate trisomy Offer karyotype and follow-up

ultrasounds

Increased NT means increased risk,

not definitive diagnosis

Trisomy screen

(16-20 wk)

Positive At risk for trisomy or NTD Basic ultrasound for dates; if dates confirmed, offer genetic amniocentesis

Most common reason for abnormal

serum screening—wrong dates

1-h diabetic screen

(26-28 wk)

Positive

(elevated)

May indicate gestational diabetes Go to 3-h GTT About 15% of those screened will

be positive

3-h glucose tolerance test 2 abnormal

values

Gestational diabetes Try ADA diet, monitor blood sugars, if

elevated may need meds or insulin

About 15% of abnormal 1-h GCT

will have gestational diabetes

GBS culture

(35-37 wk)

Positive GBS colonizing genital tract Penicillin during labor Helps to prevent early GBS sepsis of

newborn

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Table 28–3 • ANTENATAL, INTRAPARTUM, AND POSTPARTUM CASE

CORRELATION

Pregnancy Phase Condition Diagnosis Case Number

PRENATAL

Normal Routine prenatal care 28

Vaginal bleeding

<20 wk gestation

Threatened and spontaneous

abortion, ectopic pregnancy,

septic abortion

42, 43, 45

Vaginal bleeding

>20 wk’ gestation

Placenta previa, placenta

abruption

10, 11

Serum screening Congenital anomalies 7

Multiple gestations Twin gestation 8

Anemia in pregnancy Thalassemia 2

Abdominal pain in

pregnancy

Torsion of ovary, ruptured

corpus luteum

13

Hypertensive disease Preeclampsia 16

Pruritus Cholestasis of pregnancy 14

Thromboembolism DVT in pregnancy,

pulmonary embolism

15

Thyroid disease Hyperthyroidism in

pregnancy

21

Infectious Chlamydia and HIV in

pregnancy, pyelonephritis,

Parvovirus

20, 23, 19

INTRAPARTUM

Labor Normal and abnormal 1

Fetal heart rate Fetal bradycardia 5

Preterm birth Preterm labor 17

Infection Intra-amniotic infection, HSV

in labor

18, 9

DELIVERY

Complications of

delivery

Shoulder dystocia 4

Hemorrhage Placenta accreta, postpartum

hemorrhage (also under

“postpartum”)

12, 6

POSTPARTUM

Infection Breast abscess, endometritis 26, 25

Hemorrhage Postpartum hemorrhage

(also under delivery)

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COMPREHENSION QUESTIONS

28.1 A 24-year-old woman G2P0010 had a pregnancy complicated by abruptio

placentae leading to fetal death at 38 weeks’ gestation. There was no etiology found after a diligent search. Which of the following statements is most

accurate regarding this pregnancy?

A. With no etiology found, the risk of abruption in this current pregnancy

is the same as any other pregnant patient.

B. Antenatal testing with biophysical profile should be considered starting

at 34 to 35 weeks’ gestation.

C. Induction of labor should be considered at 37 to 38 weeks’ gestation.

D. Weekly ultrasound examinations screening for retroplacental hemorrhage should be considered starting at 32 weeks’ gestation.

28.2 A 27-year-old G0P0 woman is contemplating becoming pregnant. In preparation, her obstetrician conducts a preconception counseling session, assesses

rubella status, and prescribes supplemental folate. Which of the following is

the best explanation of the purpose of the supplemental folate?

A. Avoidance of megaloblastic anemia

B. Decreasing fetal anomalies

C. Enhancing absorption of iron

D. Increasing maternal immune function

28.3 A 32-year-old G1P0 woman at 15 weeks’ gestation is a physiologist, and is

questioning the physician about the adaptations that occur in pregnancy.

Which of the following statements is most accurate regarding the changes in

pregnancy?

A. Cardiac output is largely the same as the nonpregnant woman.

B. The plasma volume is increased by about 50%.

C. The systemic vascular resistance of a pregnant woman is slightly increased

as compared to the nonpregnant woman.

D. The pregnant woman typically has a short diastolic murmur which is

physiologic.

28.4 A 29-year-old G1P0 woman at 18 weeks’ gestation is noted to have a blood

type of O, Rh-positive. Her antibody screen (indirect Coombs) is positive.

Identification of the antibody is anti-Lewis. Which of the following is the

most accurate statement regarding this patient?

A. This fetus is at significant risk for fetal erythroblastosis if she/ he is

Lewis-positive.

B. The father of the baby’s Lewis antigen status should be evaluated.

C. Ultrasound for fetal hydrops should be performed.

D. Further testing is not indicated in this patient.

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28.5 A 31-year-old G1P0 woman at 15 weeks’ gestation is noted to have a positive

hepatitis B surface antigen. Which of the following would most significantly

increase the risk of vertical transmission?

A. Presence of positive hepatitis E antigen

B. Presence of positive antihepatitis B surface antibody

C. Presence of positive antihepatitis B core antibody

D. Presence of elevated liver function tests

28.6 A 31-year-old G2 P1001 woman is at 30 weeks’ gestation and her obstetrician recommends that she receives the TdaP vaccine. The physician explains

that this is to help prevent neonatal pertussis. The patient states that she

received the vaccine after delivery of her first baby. Which of the following is

the best next step?

A. If the patient received the TdaP vaccine within the last 5 years, no vaccine

is needed.

B. If the patient received the TdaP vaccine at any time in her adult life, no

vaccine is needed.

C. The vaccine should not be administered until postpartum.

D. The vaccine should be given regardless of whether has previously been

given.

ANSWERS

28.1 C. A history of abruption that is unexplained confers an increased risk of

abruption with subsequent pregnancies. Antenatal testing does not predict

acute events such as abruption. Rather, fetal testing such as biophysical profile is designed to identify chronic uteroplacental insufficiency such as caused

by chronic hypertension, renal insufficiency, or maternal lupus. Ultrasound

has poor ability to identify retroplacental clots or abruption. Induction at or

slightly before the time of abruption with the fetal loss, if at term, is a reasonable approach to avoid repeat abruption.

28.2 B. The main purpose of the supplemental folate prior to pregnancy is to help

reduce fetal neural tube defects (NTDs). These conditions include anencephaly, a fatal anomaly where there are no cerebral hemispheres or fetal skull, or

spina bifida which often leads to debilitation and inability to control bowel

or bladder. Because the neural tube closes at 21 to 28 days embryonic age

(5-6 weeks’ gestational age), by the time the patient realizes she is pregnant,

the “die is cast” regarding the neural tube. Folate supplementation reduces the

risk of neural tube defects by 50%; thus, every woman in the reproductive age

should take sufficient folate to reduce the risk of fetal NTDs.

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28.3 B. In pregnancy, the plasma volume is increased by about 50%. The cardiac

output likewise increases by 50%, as does the glomerular filtration rate.

Both the stroke volume and heart rate increase to account for this elevated

CO. The mean arterial pressure is unchanged to slightly decreased, meaning

that the systemic vascular resistance is markedly decreased as compared to

the nonpregnant patient. An early systolic ejection murmur is physiologic,

whereas a diastolic murmur usually indicates a pathological etiology.

28.4 D. No further testing is indicated in this patient, because anti-Lewis antibodies do not cause hemolytic disease of the newborn. This is because Lewis

antibodies are IgM and do not cross the placenta, whereas anti-D (Rh) are

IgG. Other worrisome antibodies include anti-Kell and anti-Duffy. “Lewis

lives, Kell kills, Duffy dies.” This highlights the need to identify the antibody

when the indirect Coombs (antibody screen) is positive. When a worrisome

antibody is identified, the titer should be evaluated to assess the potential

severity of the isoimmunization potential. In general, fetal risk is not great

unless the titer is 1:8 or higher.

28.5 A. This patient has a positive hepatitis B surface antigen, meaning that the

patient has been infected with hepatitis B virus and currently still infectious

(virus actively replicating). Liver function tests would indicate whether this

is a chronic carrier status (normal LFT ) versus active hepatitis (elevated

LFT ). The hepatitis antibodies also will give a clue regarding acute versus

chronic hepatitis. The presence of hepatitis Be antigen markedly increases

the transmission. Regardless of whether E antigen is present, this baby when

born should receive hepatitis B immune globulin to protect against immediate exposure, and then the active hepatitis B vaccine for lifelong immunity.

Hepatitis B infections to the neonate often lead to cirrhosis and hepatocellular carcinoma.

28.6 D. The TdaP vaccine is a killed vaccine and is safe in pregnancy. It should

be given between 28 and 36 weeks’ gestation regardless of whether it has

been given in prior pregnancies. The reason is so that the patient will augment an IgG antibody response, which will result in passive transmission to

the fetus. This is the mechanism for reducing the risk of neonatal pertussis.

Other adults who will be near the newborn such as spouses, grandparents,

older siblings, or babysitters should also be vaccinated to reduce the risk of

their acquisition of pertussis.

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REFERENCES

Cunningham FG, Leveno KJ, Bloom SL, H auth JC, Gilstrap LC III, Wenstrom KD. Prenatal care.

In: Williams Obstetrics. 24th ed. New York, NY: McGraw-H ill; 2014:201-230.

Lu MC, Williams III, J, H obel CJ. Antepartum care: preconception and prenatal care, genetic evaluation

and teratology, and antenatal fetal assessment. In: H acker NF, Gambone JC, H obel CJ, eds. Essentials

of Obstetrics and Gynecology. 5th ed. Philadelphia, PA: Saunders; 2009:71-90.