I hate to be on the side of the medical establishment on this one, but there are occasionally babies who do get severe hemorrhage if they don't get vitamin K. The incidence is probably low, but it is not rare, and older pediatricians do remember babies having severe gi bleeding within the first week of life secondary to vitamin K deficiency. I myself, though I am obviously still young (51), have seen babies present with intracranial hemorrhages which tend to occur later, about 6 weeks after birth. Two, I think, but it was devastating. So, did mother nature goof on this one? No, probably not. In the state of nature, babies were exposed to all sorts of bacteria which infected their guts despite breastfeeding (though the numbers were kept down), and these bugs produced vitamin K, as they do in artificially fed babies. Or, it is possible, that such a relatively uncommon event would not really be evolutionarily disadvantageous. The question of vitamin K and leukemia has pretty well been put to rest. I would get the vitamin K. It's not such a big deal. Jack Newman, MD, FRCPC