Positive evidence of fetus risks but benefits may outweigh risks in some cases
How it works
Mechanism information is still being processed. Check the DailyMed link in the sidebar for the official prescribing information.
Dosing & administration
Dosing varies by indication and patient profile. Always follow your institution's current prescribing guidelines.
Renal impairment
Consult protocols for adjustment.
Liver impairment
Consult protocols for adjustment.
Use during pregnancy
1st trimester
Critical teratogenic risk between 6–9 weeks (Fetal Warfarin Syndrome). Discontinue before conception or as soon as pregnancy is confirmed.
2nd trimester
Risk of CNS malformations and fetal hemorrhage. Avoid.
3rd trimester
High risk of fetal and neonatal hemorrhage, particularly at delivery. Switch to heparin (UFH) by 36 weeks.
Clinical note
Contraindicated in most circumstances. Warfarin is a proven human teratogen. Exposure between 6–9 weeks gestation causes Fetal Warfarin Syndrome: nasal hypoplasia, stippled epiphyses, and limb defects in approximately 5% of exposed fetuses. Any trimester exposure carries risk of fetal intracranial hemorrhage due to anticoagulation of the fetal blood. Exception: women with mechanical heart valves may require warfarin due to inadequate LMWH valve protection — this requires individualized multidisciplinary decision-making.
Breastfeeding
Safe during breastfeeding. Warfarin is highly protein-bound and is not detected in clinically significant amounts in breast milk. Compatible with breastfeeding.
