Updated: 1/26/2022

Prenatal Care

Review Topic
  • Snapshot
    • A 26-year-old G1P0 woman presents to the obstetrician for her first prenatal visit. An ultrasound is performed (See image). She is estimated to be approximately 8 weeks gestation. She notes that she has experienced increased fatigue and occassional nausea but no major complaints. The patient is a recent immigrant from Mexico and has no immunization records with her and does not recall her vaccination history. She is sexually active with only her husband and has no history of sexually transmitted infections. The obstetrician takes a thorough medical history, performs a physical examination, informs her about the course of pregnancy, and explains details of the laboratory studies that will be performed at the current visit and subsequent visits.
  • Introduction
    • Overview
      • prenatal care helps to ensure the birth of a healthy baby while also maintaining a healthy pregnancy for the mother
        • accurate estimation of gestational age
        • identify pregnancies at ↑ risk for maternal or fetal morbidity/mortality
        • prevent morbidity during pregnancy
        • provide a transition to a healthy labor and birth
    • Timing
      • initial prenatal visit at 8-10 weeks of pregnancy
        • earlier if at risk for ectopic pregnancy
      • subsequent prenatal visits
        • every 4 weeks for the first 28 weeks
        • every 2-3 weeks until 36 weeks gestation
        • every week after 36 weeks gestation
    • Initial prenatal visit
      • assessment
        • initial history and physical exam
        • family medical history
        • genetic history
        • general examination to confirm pregnancy
        • assess for tobacco, alcohol, and/or drug use
        • screen for domestic violence
        • screen for depression
        • provide prescriptions for prenatal vitamins and iron supplementation
      • education/counseling
        • inform about expected course of pregnancy
        • discuss recommendation for 30 minutes of moderate-intensity exercise 5-7 days a week
          • avoid contact sports or activities with high fall risk
        • discuss routine lab studies and testing
        • discuss genetic counseling and prenatal diagnostic testing
          • cystic fibrosis carrier screening
          • hemoglobinopathy screening for individuals of African, Southeast Asian and Mediterranean descent
        • discuss high-risk conditions
      • routine lab/diagnostic studies
        • blood type and screen
        • complete blood count (CBC)
        • platelet count
        • hepatitis B surface antigen (HBsAg)
        • syphilis screening test
        • screening for gestational diabetes if at high risk
          • risk factors for gestational diabetes mellitus
            • pre-pregnancy BMI ≥ 30 kg/m
            • previous history of gestational diabetes
        • cervical cancer screening
          • Pap test
        • urine dipstick for protein and glucose levels
        • urine culture and sensitivity test
          • asymptomatic bacteriuria should be treated in pregnant women
        • chlamydia screening
        • gonorrhea screening for women at risk for sexually transmitted infections
          • risk factors for sexually transmitted infections
            • age < 25 years
            • previous sexually transmitted infection
            • new or multiple sex partners
            • inconsistent condom use
            • commercial sex work
        • rubella titer
          • if not already immune, do not administer vaccine during pregnancy
            • MMR (measles, mumps, and rubella) is a live vaccine
        • TSH
          • hypothyroid women should have their dose of levothyroxine increased if found to be pregnant
            • during pregnancy, ↑ circulating levels of thyroxine-binding globulin (TBG), and ↑ plasma volume ↑ demand for T4
        • inactivated influenza vaccination
    • Subsequent prenatal visits
      • every visit
        • vital signs
        • weight
        • fetal assessment, beginning after 10 weeks gestation
        • uterine size assessment (see Table below)
        • domestic violence screening
        • assessment of tobacco use and exposure
        • urine dipstick for protein and glucose levels
      • weeks 11-14 of pregnancy
        • education about breastfeeding
        • screening tests for aneuploidy
          • women with ↑ risk for aneuploidy
            • offer option of chorionic villus sampling or 2nd trimester amniocentesis
      • weeks 15-20 of pregnancy
        • anatomic survey ultrasound at 18-20 weeks
        • neural tube defect screening
          • maternal serum alpha-fetoprotein (MSAFP)
      • weeks 24-28 of pregnancy
        • repeat type and screen
          • if Rh negative, administer Rh immunoglobulin
        • screen for gestational diabetes
        • discuss postpartum contraception
      • weeks 32-34 of pregnancy
        • repeat testing for women at ↑ risk for sexually transmitted infections
          • syphilis, HIV, gonorrhea, and chlamydia
      • week 36 of pregnancy
        • determine fetal position
        • group B strep screening
      • week 38 of pregnancy
        • provide information about labor
        • discuss postpartum contraception again
      • > 41 weeks of pregnancy
        • discuss labor induction   
    • Estimating Gestational Age by Uterine Size
      12 weeks
      • At pubic symphysis
      16 weeks
      • Midway from symphysis to umbilicus
      20 weeks
      • At umbilicus
      20-36 weeks
      • Height (in cm) above pubic symphysis correlates with weeks of gestation
      • Timing of Major Prenatal Tests
      • Prental Test
      • Gestational Age (Weeks)
      • Details of test
      • First trimester screen
      • 11-14
      • Ultrasound for nuchal translucency
      • PAPP-A
      • ↓ levels are seen in chromosomal abnormalities
      • hCG
      • ↑ levels are seen in chromosomal abnormalities
      • Cell free fetal DNA
      • ~10
      • Analyze fetal DNA in maternal blood
      • Screens for trisomies of 13, 18, and 21
      • Positive test results should be followed by CVS or amniocentesis
      • Chorionic villus sampling (CVS)
      • 11-14
      •   Collect placental tissue to test for chromosomal and genetic abnormalities
      • Quadruple screen
      • 16-18
      • AFP, hCG, estriol, and inhibin
      •   ↑ AFP = neural tube or abdominal wall defects
      • ↑ hCG and inhibin and↓ AFP and estriol = Down syndrome
      • ↓ AFP, hCG, and estriol = Edwards syndrome
      • Amniocentesis
      • 15-20
      • Collect amniotic fluid to diagnosis chromosomal abnormalities
      • Glucose challenge test
      • 24-28
      • 1 hr glucose challenge test
      • If abnormal followed by glucose tolerance test
      • Group B strep test
      • 35-37
      • Swab the lower genital tract for colonization by GBS

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(M2.OB.17.4870) An 18-year-old G1P0 woman who is 10 weeks pregnant presents for her first prenatal visit. She reports nausea with occasional vomiting but denies bleeding, urinary symptoms, or abdominal pain. She just graduated high school and works at the local grocery store. She does not take any medications and has no known drug allergies. Physical examination is unremarkable. Initial laboratory studies reveal the following:

Na+: 140 mEq/L
Cl-: 100 mEq/L
K+: 4.0 mEq/L
HCO3-: 24 mEq/L
BUN: 10 mg/dL
Glucose: 100 mg/dL
Creatinine: 1.0 mg/dL
Thyroid-stimulating hormone: 2.5 µU/mL
Ca2+: 9.5 mg/dL
AST: 25 U/L
ALT: 20 U/L

Leukocyte count: 10,000 cells/mm^3 with normal differential
Hemoglobin: 14 g/dL
Hematocrit: 42%
Platelet count: 200,000 /mm^3

Epithelial cells: few
Glucose: negative
WBC: 20/hpf
Bacterial: > 100,000 cfu / E. coli pan-sensitive

What is the best next step in management?

QID: 109565

Observation and treatment if symptoms develop



Nitrofurantoin for seven days



Observation and repeat cultures in one week



Nitrofurantoin for duration of pregnancy



Levofloxacin for three days



M 7 D

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(M2.OB.15.4672) A 33-year-old G1P0 at 32 weeks gestation presents to her OB/GYN for a prenatal check-up. Her medical history is significant for type II pregestational diabetes mellitus, which has been well-controlled with diet and insulin so far throughout her pregnancy. Which of the following is the recommended future follow-up for this patient?

QID: 107200

Ultrasound for fetal growth every week starting now until delivery



Monitor fetal kick counts starting now until 40 weeks gestation



Monthly nonstress test strating at 34 weeks gestation until delivery



Monthly biophysical profile now until delivery



Twice weekly nonstress test now until delivery



M 8 E

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(M2.OB.15.4672) A 32-year-old G3P2 at 20 weeks gestation presents to her PCP with complaints of fatigue, chills, and decreased appetite for the past 5 days. Her pregnancy has been uncomplicated to-date, and she has been receiving regular prenatal care. The patient mentions that, in an attempt to increase nutrition for her fetus, she has been consuming increased amounts of dairy products in the past month. At 35 weeks gestation, the patient delivers an ill neonate with sepsis, pneumonia, and disseminated skin findings (Figure A). What is the appropriate action that the PCP should have taken after the patient’s initial presentation?

QID: 107192

Supportive care with rest and hydration



Blood and amniotic fluid cultures



Vaginal and stool cultures



Empiric ceftriaxone therapy



Empiric ampicillin therapy



M 6 E

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(M2.OB.15.4672) A 27-year-old G0P0 female presents to her OB/GYN for a preconception visit to seek advice before becoming pregnant. A detailed history reveals no prior medical or surgical history, and she appears to be in good health currently. Her vaccination history is up-to-date. She denies tobacco or recreational drug use and admits to drinking 2 glasses of wine per week. She states that she is looking to start trying to become pregnant within the next month, hopefully by the end of January. Which of the following is NOT recommended as a next step for this patient's preconception care?

QID: 107199

Begin 400 mcg folic acid supplementation



Recommend inactivated influenza vaccination



Obtain rubella titer



Administer measles, mumps, rubella (MMR) vaccination



Obtain varicella zoster titer



M 8 E

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(M2.OMB.5662) A 28-year-old G1P0 woman presents to the clinic to initiate prenatal care after a positive home pregnancy test. The first day of her last menstrual period was 7 weeks prior to presentation. Her menstrual cycle is regular and occurs every 28 days. The patient has no medical conditions or a history of surgery. She takes no medications. Her temperature is 98.6°F (37.0°C), blood pressure is 110/70 mmHg, pulse is 64/min, and respirations are 17/min. Physical exam is notable for a nontender abdomen. Pelvic exam reveals a closed cervix with no adnexal or uterine tenderness. A urine pregnancy test is positive, and an intrauterine singleton pregnancy measuring approximately 9 weeks gestational age is visualized on transabdominal ultrasound. During counseling, the patient asks if she should modify her current exercise regimen due to her pregnancy. She typically swims or uses an exercise bike for 45 minutes, 5 days a week, and plays in an office soccer league for 1 hour on 1 day per week. Which of the following is the most appropriate recommendation regarding exercise during pregnancy for this patient?

QID: 216262

Avoid exercise during pregnancy



Avoid soccer during pregnancy, continue other activities



Continue the current exercise regimen



Limit moderate exercise to a maximum of 30 minutes per day during pregnancy



Reduce to walking only, beginning in the third trimester



M 7 E

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