Vitamin K1 in the newborn.

By a sensitive high-performance liquid chromatography method it was possible to measure vitamin K1 concentrations in mothers and their newborn children, even at a level of 0.5 nmol/l. All neonates were born after an uncomplicated and full-term pregnancy. The vitamin K1 concentration in neonates proved to be about half the value of their mothers, which is consistent with earlier studies of vitamin K1 dependent clotting factors. One may assume the existence of a partial placental barrier to vitamin K1. Venous, arterial and mixed cord blood did not differ significantly, so puncturing the vena umbilicalis is sufficient to measure vitamin K1 concentrations in cord blood.