This is still a fairly rare phenomenon in my hospital, but it does seem to increasing slightly here, as it is just about everywhere else. The science is settled, transplacental transfer of vitamin K is extremely limited, hepatic stores at birth are very low, and human milk contains extremely low concentrations of vitamin K. In later life, most of our vitamin K2 is produced by intestinal microbiota, including by our friends the Bifidobacteria, as well as Bacteroides and Prevotella, but we don't have many of those present at birth or over the first few days.