Excretion of low molecular weight heparin in human milk

Abstract

Aims: The excretion of low molecular weight heparin (LMWH) in breast milk was investigated in 15 lactating mothers after Caesarean section. Methods: Blood and milk samples were collected before and 3-4 h after once daily routine subcutaneous injection of 2500 IU dalteparin. Anti-Xa activity was measured by an assay utilizing prolonged clotting times in plasma or breast milk as an index of LMWH activity. Results: Plasma anti-Xa activities ranged from 0.074 to 0.308 IU ml-1 of plasma. Anti-Xa activities in breast milk ranged from <0.005-0.037 IU ml-1 of milk. This is equivalent to a milk/plasma ratio of <0.025-0.224. Conclusions: Therefore, it appears highly unlikely that puerperal thromboprophylaxis with LMWH has any clinically relevant effect on the nursing infant.