OB/GYN
Routine Prenatal Care Timeline
OB/GYN

Routine Prenatal Care Timeline

Visit-by-visit prenatal labs and screening.

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◆Initial visit (8–10 weeks)

  • •Labs: CBC, blood type + Rh + antibody screen, HIV, syphilis (RPR/VDRL), HBsAg, anti-HCV, rubella IgG, varicella IgG, urine culture (asymptomatic bacteriuria), urinalysis (protein)
  • •STIs (chlamydia + gonorrhea) if <25 or high-risk
  • •Pap if due
  • •Confirm dating with US
  • •Naegele rule: LMP + 7 days − 3 months + 1 year

◆10–13 weeks

  • •Nuchal translucency + PAPP-A + β-hCG (first trimester aneuploidy screen)
  • •Cell-free DNA option from 10 weeks
  • •CVS if diagnostic indicated

◆15–20 weeks

  • •Quad screen (AFP + β-hCG + estriol + inhibin A)
  • •Amniocentesis if diagnostic needed

◆18–20 weeks

  • •Anatomy ultrasound

◆24–28 weeks

  • •1-hour 50 g glucose challenge (GDM screen); if ≥140 → 3-hr 100 g OGTT
  • •Repeat antibody screen if Rh-negative

◆27–36 weeks

  • •Tdap (each pregnancy)
  • •RSV vaccine (32–36 weeks)

◆28 weeks

  • •RhoGAM (Rh-negative + unsensitized)

◆35–37 weeks

  • •Group B Strep (GBS) rectovaginal swab

◆3rd trimester repeat (if high-risk)

  • •Repeat STIs (chlamydia, gonorrhea, HIV, syphilis) if <25 or high-risk

High-yield pearls

  • ◆Naegele rule for EDC
  • ◆GTPAL: Gravidity, Term, Preterm, Abortion, Living
  • ◆β-hCG doubles q48h in early IUP; lagging = ectopic
  • ◆Discriminatory zone: β-hCG >1500–2000 + empty uterus → ectopic
  • ◆Tdap each pregnancy 27–36 weeks; passive antibody transfer
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