Is Warfarin Sodium Absolutely Contraindicated During Lactation?

There is widespread concern regarding the secretion of a variety of drugs and toxins into human milk. A survey of the practices of obstetricians and neonatologists at 2 teaching medical centers regarding the appropriateness of allowing a mother on warfarin sodium to breast feed her infant revealed that almost all advised such mothers against breast feeding. This study reports the data on two mother- infant pairs who were evaluated with Prothrombin time activity (Protime), Factor II (FII) and Factor VII/X (FVII) levels simultaneously while the mothers were on warfarin sodium and the infants were exclusively breast fed. Both mothers had extensive serious venous thromboembolic disease necessitating the administration of anticoagulants; warfarin sodium was first started in both mothers in the post-partum period.

The prothrombin time activities on the first mother-infant pair, on blood samples drawn simultaneously are shown below.

Breast milk extracted from this mother on one occasion did not reveal any warfarin sodium by a spectrophotometric assay. Data on the second mother-infant pair on blood samples obtained simultaneously were as follows.

These data demonstrate conclusively that there is no inhibition of the coagulation mechanism in normal full term infants when they are breast fed by mothers who are therapeutically anticoagulated with warfarin sodium.