Warfarin
Vitamin K Antagonist Anticoagulant
Warfarin freely crosses the placenta and is a potent teratogen during weeks 6–12 of gestation. Causes Fetal Warfarin Embryopathy (nasal hypoplasia, stippled epiphyses, microcephaly, optic atrophy) and fetal central nervous system/intrauterine hemorrhage in 2nd and 3rd trimesters.
FDA Black Box Warning: Warfarin is contraindicated in pregnancy. Discontinue immediately upon pregnancy detection and switch to Low Molecular Weight Heparin (Enoxaparin).
Causes Fetal Warfarin Syndrome / Embryopathy (nasal hypoplasia, skeletal stippling).
Risk of fetal CNS anomalies, optic atrophy, and microcephaly.
High risk of fatal fetal hemorrhage and peripartum maternal/fetal bleeding.
Inhibits fetal vitamin K-dependent clotting factors (II, VII, IX, X) and fetal bone matrix proteins.
Nasal hypoplasia (depressed nasal bridge), stippled epiphyses, brachydactyly, and severe intrauterine growth restriction.
Fetal anticoagulation leads to central nervous system hemorrhage, optic atrophy, and fetal demise.
Maternal hemorrhage, placental abruption, and fatal bleeding during delivery.
Discontinue warfarin immediately upon pregnancy detection and switch to therapeutic Low Molecular Weight Heparin (Enoxaparin / Clexane).
Stop taking warfarin immediately and contact your OB/GYN or hematologist to switch to enoxaparin injections.
- Immediate transition to enoxaparin
- Level II targeted fetal anatomical ultrasound
- FDA Black Box Warning against warfarin use in pregnancy (Category X).
Warfarin (Coumadin) is not safe during pregnancy because it crosses to your baby and causes serious birth defects and bleeding. Your doctor will switch you to enoxaparin injections instead.
Warfarin causes severe birth defects (Fetal Warfarin Syndrome) and dangerous bleeding in the baby.
FDA Black Box Warning and well-characterized Fetal Warfarin Syndrome.
-
1
U.S. Food and Drug Administration (FDA) PLLR — FDA Pregnancy and Lactation Labeling Rule & Approved Prescribing Information Database Last updated: Official FDA Standard
-
2
FDA Center for Drug Evaluation and Research (CDER) — FDA MedWatch & Black Box Warning Database Last updated: Official FDA Standard
-
3
ACOG Practice Bulletins & Guidelines — American College of Obstetricians and Gynecologists Clinical Recommendations Last updated: 2025 Clinical Edition
-
4
Briggs Drugs in Pregnancy and Lactation — Reference Guide to Fetal and Neonatal Risk (12th Edition) Last updated: 2025 Clinical Edition