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Prenatal Care and Testing

BASICS

  • Goal: Ensure maternal and fetal well-being through evidence-based, patient-centered care.
  • Core principles: Accurate gestational age, risk identification, maternal empowerment, timely intervention for fetal/maternal complications.

GENERAL PREVENTION

  • Standard visit schedule (USA):
  • Monthly: Weeks 4–28
  • Twice monthly: Weeks 28–36
  • Weekly: After 36 weeks until delivery

DIAGNOSIS

History (Initial and Ongoing)

  • Medical: DM, obesity, thyroid, HTN, age, DVT/PE, uterine anomalies, autoimmune disease, family history of inherited/gestational conditions
  • Obstetric: Preterm delivery, preeclampsia, gestational diabetes, SCD, previous newborn with birth defect/genetic syndrome
  • Psychosocial: Depression/mental health, intimate partner violence (screen at least 1x/trimester + postpartum), substance use, lifestyle, travel, exposures, barriers to care

Physical Exam

  • Full exam at intake; at each visit, document:
  • Weight (IOM recommendations by BMI)
  • BP
  • Fundal height (from 20–24 weeks)
  • Fetal heart rate (8–12 weeks by Doppler)
  • Pelvic/cervical exam if indicated
  • Fetal position (Leopold maneuver, 32–36 weeks)

Weight Gain (2009 IOM)

  • BMI <18.5: 28–40 lb
  • BMI 18.5–24.9: 25–35 lb
  • BMI 25–29.9: 15–25 lb
  • BMI ≥30: 11–20 lb

DIAGNOSTIC TESTS & INTERPRETATION

First Prenatal Visit

  • Hct/Hgb, blood type, Rh, antibody screen
  • Hemoglobin electrophoresis (sickle cell/thalassemia)
  • Urine culture
  • Rubella & varicella antibody titers
  • STI screen: RPR/VDRL, GC/C, HepB, HIV
  • Carrier screening: Cystic fibrosis, SMA, hemoglobinopathies (offer counseling)
  • Aneuploidy screening: Offer all women; includes nuchal translucency (NT), hCG, PAPP-A, quad screen (AFP, UE3, hCG, DIA), cell-free DNA (not diagnostic)
  • Cervical cancer screening: Pap/HPV as per guidelines (age ≥21), colposcopy/biopsy guidelines per lesion and gestation

Subsequent Visits

  • Urinalysis (glucose, protein; baseline useful in high-risk)
  • 24–28 weeks: Diabetes screen, repeat Hct/Hgb, antibody screen (Rh-negative), repeat syphilis, repeat HIV (high-risk), nutrition and lifestyle counseling
  • 35–37 weeks: GBS screen, high-risk STI screen
  • Postterm (>41–42 weeks): Assess fetal well-being with NST/US

Gestational Diabetes Screening

  • Early screen if high-risk (BMI ≥25 + risk factors)
  • Standard: 2-step (1-hr glucola, then 3-hr GTT if positive) at 24–28 weeks
  • Diagnosis: ≥2 positive GTT values (NDDG or Carpenter & Coustan standards)
  • 1-step (75g OGTT) also used in some centers

Other Key Labs/Procedures

  • US: Nuchal translucency (11–13 wks), anatomic survey (18–22 wks)
  • CVS (10–12 wks), amniocentesis (15–18 wks) if indicated
  • Chromosomal microarray if fetal abnormality suspected

IMMUNIZATIONS

  • Tdap (27–36 wks, every pregnancy)
  • Hepatitis B
  • Influenza
  • COVID-19 (recommended)
  • Avoid live vaccines (MMR, varicella, BCG)

NUTRITION & SUPPLEMENTS

  • Folic acid: 0.4 mg/day (preconception and during pregnancy), 1–4 mg/day for high risk
  • Calcium: 1,000–1,300 mg/day
  • Vitamin D: 200–1,200 IU/day (prenatal vitamin dose)
  • Iron: Supplement if needed for anemia
  • Vitamin A: <5,000 IU/day
  • Limit caffeine: <200 mg/day
  • Avoid high-mercury fish (shark, tuna, swordfish, mackerel)

LIFESTYLE & COUNSELING

  • Travel: Safe until week 35; immobility >2 hours ↑ thrombosis risk
  • Exercise: Continue if uncomplicated
  • Seatbelts/airbags: Use both
  • Sexual activity: Safe unless contraindicated (placenta previa, etc.)
  • Alcohol, tobacco, illicit drugs: Avoid
  • Medication safety: Review all drugs for teratogenicity

SPECIAL SITUATIONS

  • GDM history: Annual diabetes screening postpartum (50% risk for type 2 DM over 20 years)
  • Abnormal labs/imaging: Refer to MFM or specialty care

PROGNOSIS

  • Routine prenatal care reduces perinatal morbidity/mortality

ICD-10 CODES

  • Z34.90 Encounter for supervision of normal pregnancy, unspecified trimester
  • Z36 Encounter for antenatal screening
  • Z34.00 Encounter for supervision of normal first pregnancy, unspecified trimester

CLINICAL PEARLS

  • Checklists/team-based care increase adherence to best practices
  • Early, consistent prenatal care is key for good outcomes
  • Shared decision-making: Offer all women screening/diagnostic options regardless of age/risk