Because of the very low milk levels with warfarin doses up to at least 12 mg daily, amounts ingested by the infant are small. No adverse reactions in breastfed infants have been reported from maternal warfarin use during lactation, even with a dose of 25 mg daily for 7 days. There is a consensus that maternal warfarin therapy during breastfeeding poses little risk to the breastfed infant.[1,2] No special precautions are necessary.
Women’s postpartum warfarin dosage requirements may be increased by as much as two-fold compared to prepregnancy requirements. Whether breastfeeding contributes to the increased requirement is unclear.[3]