Can I take warfarin while pregnant or breastfeeding?

8.1 Pregnancy Risk Summary Warfarin sodium tablets, USP are contraindicated in women who are pregnant except in pregnant women with mechanical heart valves, who are at high risk of thromboembolism, and for whom the benefits of warfarin sodium may outweigh the risks [see Warnings and Precautions (5.7) ]. Warfarin sodium can cause fetal harm. Exposure to warfarin during the first trimester of pregnancy caused a pattern of congenital malformations in about 5% of exposed offspring. Because these data were not collected in adequate and well-controlled studies, this incidence of major birth defects is not an adequate basis for comparison to the estimated incidences in the control group or the U.S. general population and may not reflect the incidences observed in practice. Consider the benefits and risks of warfarin sodium and possible risks to the fetus when prescribing warfarin sodium to a pregnant woman. Adverse outcomes in pregnancy occur regardless of the health of the mother or the use of medications. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown.

Prescribing label, section “8.1 Pregnancy” (opening excerpt): Warfarin Sodium (oral), Cardinal Health 107, LLC. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.

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]

“Summary of Use during Lactation”, LactMed record “Warfarin” (LM279), quoted verbatim. Everything LactMed reports about Warfarin while breastfeeding.

8.2 Lactation Risk Summary Warfarin was not present in human milk from mothers treated with warfarin from a limited published study. Because of the potential for serious adverse reactions, including bleeding in a breastfed infant, consider the developmental and health benefits of breastfeeding along with the mother's clinical need for warfarin sodium and any potential adverse effects on the breastfed infant from warfarin sodium or from the underlying maternal condition before prescribing warfarin sodium to a lactating woman.

Prescribing label, section “8.2 Lactation” (opening excerpt): Warfarin Sodium (oral), Cardinal Health 107, LLC. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.