[Vitamin K deficiency in the newborn].

Newborns have low levels of the vitamin K dependent clotting factors. Early studies were suggestive of vitamin K deficiency. Recently these findings were questioned by studies that failed to detect signs of vitamin K deficiency in the clotting system of newborns using more specific methods, while other studies did find signs of vitamin K deficiency using the same methods. The question was finally solved by direct measurement of vitamin K showing very low levels of the vitamin in the serum of newborns immediately after birth. Whether vitamin K supplementation to the mother reduces the incidence of vitamin K induced changes in the clotting system of newborns remains to be elucidated. In the meantime it seems prudent to administer parenteral vitamin K prophylactically to all newborns immediately after birth.