OB/GYN
Teratogens & Medications in Pregnancy
OB/GYN

Teratogens & Medications in Pregnancy

High-yield teratogenic patterns.

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Hyperthyroidism in pregnancy

  • 1st trimester: PTU (methimazole = cutis aplasia)
  • 2nd/3rd trimester: methimazole (long-term PTU = hepatotoxicity)
  • Radioactive iodine: ABSOLUTELY CONTRAINDICATED
  • Propranolol for symptoms

DVT/PE in pregnancy

  • LMWH preferred (does not cross placenta)
  • AVOID warfarin and DOACs
  • Switch to UFH near delivery

Hypertension in pregnancy

  • Safe: 'HMLN' — Hydralazine, Methyldopa, Labetalol, Nifedipine
  • Avoid: ACEi, ARBs, atenolol, diuretics (preeclampsia)

Vaccines

  • SAFE: inactivated influenza, Tdap (27–36 wks), Hep A/B (high-risk), RSV (32–36 wks)
  • CONTRAINDICATED (live): MMR, varicella, intranasal flu
  • HPV: not given in pregnancy

Classic teratogens

DrugEffect
ACE inhibitors / ARBsRenal agenesis → Potter sequence, oligohydramnios
WarfarinNasal hypoplasia + stippled epiphyses (fetal warfarin syndrome)
Isotretinoin (vit A)Severe craniofacial + CNS + cardiac (use iPLEDGE)
MethotrexateAminopterin syndrome — limb + craniofacial defects
LithiumEbstein anomaly (tricuspid valve)
Methimazole (1st trim)Cutis aplasia (absence of skin); choanal/esophageal atresia
PhenytoinFetal hydantoin syndrome (cleft lip/palate, cardiac defects)
ValproateNeural tube defects (highest risk anticonvulsant)
CarbamazepineNeural tube defects + craniofacial
TetracyclinesTooth discoloration + bone growth inhibition
FluoroquinolonesCartilage damage
AminoglycosidesOtotoxicity (CN VIII)
NSAIDs (3rd trim)Premature ductus arteriosus closure + oligohydramnios
ThalidomidePhocomelia (limb defects)
DES (historical)Clear cell adenocarcinoma of vagina in daughters
AlcoholFetal alcohol syndrome (FAS) — facial dysmorphism, growth restriction, neuro
CocainePlacental abruption, IUGR, neonatal stroke
TobaccoIUGR, preterm birth, placental abruption

High-yield pearls

  • ACEi/ARB → Potter sequence
  • Methimazole 1st trim → cutis aplasia (use PTU)
  • Lithium → Ebstein anomaly
  • Valproate → highest NTD risk among anticonvulsants
  • NSAIDs 3rd trim → premature ductus closure
  • Mom on isotretinoin: 2 forms of contraception + monthly pregnancy tests
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