Is anticoagulation (blood thinner) therapy compatible with breastfeeding?

From the Guidelines

Breastfeeding is safe for women requiring anticoagulation therapy with warfarin, acenocoumarol, or unfractionated heparin (UFH), as recommended by the American College of Chest Physicians 1.

Anticoagulation Options

The following anticoagulants are considered safe for breastfeeding mothers:

• Warfarin: due to its high protein binding and ionization, it does not pass significantly into breast milk
• Low molecular weight heparins (LMWHs) like enoxaparin and dalteparin: these large molecules cannot enter breast milk
• Unfractionated heparin: it is not orally bioavailable

Direct Oral Anticoagulants (DOACs)

DOACs are not recommended for breastfeeding women due to limited data on their safety 1. The American Society of Hematology 2018 guidelines also state that there is low certainty in evidence for the safety of using warfarin, acenocoumarol, LMWH, fondaparinux, or danaparoid while breastfeeding, and very low certainty in evidence against using direct-acting oral anticoagulants 1.

Recommendations

• Women requiring anticoagulation therapy can safely breastfeed with warfarin, acenocoumarol, or UFH
• LMWH or warfarin are preferred options for women starting anticoagulation postpartum
• DOACs should be avoided in breastfeeding women until more data is available on their safety
• Women should be counseled on the importance of adherence to medication and have regular follow-up to assess progress 1

From the FDA Drug Label

Based on very limited published data, warfarin has not been detected in the breast milk of mothers treated with warfarin The same limited published data report that some breast-fed infants, whose mothers were treated with warfarin, had prolonged prothrombin times, although not as prolonged as those of the mothers. The decision to breast-feed should be undertaken only after careful consideration of the available alternatives Women who are breast-feeding and anticoagulated with warfarin should be very carefully monitored so that recommended PT/INR values are not exceeded. It is prudent to perform coagulation tests and to evaluate vitamin K status in infants before advising women taking warfarin to breast-feed.

Warfarin has not been detected in breast milk, but breast-fed infants may have prolonged prothrombin times.

• Careful consideration is needed before breastfeeding while taking warfarin.
• Monitoring of PT/INR values and coagulation tests in infants is recommended 2.

From the Research

Anticoagulation and Breastfeeding

• The use of anticoagulants during breastfeeding is a topic of interest, with several studies investigating the safety and efficacy of these medications in lactating women 3, 4, 5.
• Warfarin is considered a compatible and recommended agent in the postpartum period and during lactation, as it is not excreted into breast milk 5.
• However, the dosage of warfarin may need to be adjusted in breastfeeding women, as one study found that a patient required a 100% increase in her warfarin dose postpartum to achieve a therapeutic international normalized ratio (INR) 3.
• Direct oral anticoagulants (DOACs) such as dabigatran, rivaroxaban, and apixaban have limited data regarding their safety during breastfeeding, but available studies suggest that dabigatran has the least excretion in human breast milk 4.
• The measurement of anticoagulant activity in patients treated with DOACs can be challenging, but studies have investigated the use of prothrombin time (PT) and international normalized ratio (INR) as screening tests 6, 7.
• One study developed a formula to estimate the anticoagulant activity of rivaroxaban using INR values, which may be useful as a screening test in situations where anti-FXa assay is unavailable 7.

Safety of Anticoagulants during Breastfeeding

• Warfarin is considered safe for use during breastfeeding, as it is not excreted into breast milk 5.
• DOACs such as dabigatran, rivaroxaban, and apixaban have limited data regarding their safety during breastfeeding, but available studies suggest that they may be excreted into breast milk to varying degrees 4.
• Further studies are needed to fully understand the safety and efficacy of anticoagulants during breastfeeding 4, 5.

Measurement of Anticoagulant Activity

• Prothrombin time (PT) and international normalized ratio (INR) can be used as screening tests to measure anticoagulant activity in patients treated with warfarin and DOACs 6, 7.
• The use of calibrated anti-FXa assays is considered the gold standard for measuring anticoagulant activity in patients treated with DOACs, but these tests may not always be available 7.
• Alternative screening tests, such as the formula developed for rivaroxaban, may be useful in situations where anti-FXa assay is unavailable 7.