Oral anticoagulants are frequently prescribed during lactation. Because these drugs could affect the hemostasis of the newborn, we did a literature search to find out whether precautions should be taken. It appeared that acenocoumarol and warfarin are not detectable in human milk. Besides the usual daily supplementation of 25 micrograms vitamin K for every breast-fed infant, precautions are not necessary. Phenprocoumon, ethylbiscoumacetate and phenindione are excreted in human milk and could affect neonatal hemostasis.