## Warfarin and Fetal Warfarin Syndrome **Key Point:** Warfarin is a vitamin K antagonist that crosses the placenta and is absolutely contraindicated in pregnancy, particularly during the first trimester. ### Fetal Warfarin Syndrome Warfarin causes a characteristic constellation of congenital abnormalities when used in the first trimester: - Nasal hypoplasia and stippled epiphyses (pathognomonic) - CNS abnormalities (midline defects, hydrocephalus) - Eye defects (optic nerve hypoplasia, cataracts) - Growth restriction - Intellectual disability **High-Yield:** The critical period for fetal warfarin syndrome is **weeks 6–12 of gestation**, when skeletal and CNS development occurs. ### Safe Anticoagulation Alternatives in Pregnancy | Drug | Mechanism | Pregnancy Safety | Notes | |------|-----------|-----------------|-------| | **Heparin** | Inhibits thrombin & Factor Xa | Safe (doesn't cross placenta) | DOC for anticoagulation in pregnancy | | **LMWH** | Selective Factor Xa inhibition | Safe | Preferred over UFH in many centres | | **Warfarin** | Vitamin K antagonist | **Contraindicated** | Crosses placenta; teratogenic | | **DOACs** | Direct thrombin/Xa inhibitors | Avoid (limited data) | Insufficient safety data | **Clinical Pearl:** If a woman on warfarin becomes pregnant, switch immediately to heparin (UFH or LMWH). If warfarin was used in the first trimester, fetal echocardiography and skeletal survey are indicated to screen for fetal warfarin syndrome. **Mnemonic — Warfarin in Pregnancy (WARP):** **W**arfarin causes **A**bnormalities (nasal hypoplasia, stippled epiphyses), **R**estriction of growth, **P**roblems with CNS and eyes.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.