The hypothesis that breastfed babies are at greater risk is not unthinkable. First of all, hemorrhagic disease is rare, so that even if some babies died from it, most did not. Second of all, we live in a society which is paranoid about cleanliness. Vitamin K is made by certain bacteria in the gut, which are growing happily in formula milieu. They don't grow in breastfeeding milieu, unless the baby is exposed to lots of bacteria (as in preindustrial societies). Also it is true that there is more vitamin K in colostrum and that many breastfed babies don't get the colostrum very well. Jack Newman, MD, FRCPC