Vitamin K is a fat-soluble vitamin necessary mainly for the formation of blood clots. Without this vitamin, bleeding would not stop. 

Vitamin K is given as an injection to newborns to prevent vitamin K deficiency bleeding, since the level of blood clotting factors of newborn babies are roughly 30–60% that of adult values. The reason for this discrepancy is due to poor transfer of the vitamin across the placenta, and thus low fetal plasma vitamin K.

Occurrence of vitamin K deficiency bleeding in the first week of the infant's life is estimated at 0.25–1.7%, with a prevalence of 2–10 cases per 100,000 births. Since the vitamin is found in human milk and supplemented in infant formula, the concentration of vitamin K naturally rises within th ...