Vitamin passage across the placenta.

A pregnant woman who has adequate nutrition available in the form of a standard diet will provide the vitamins required by the fetus for normal development. Active transport of the water-soluble vitamins plus easy oral absorption after birth insure nutritional sufficiency at any gestational age. The fat-soluble vitamins which have a much slower transfer rate as the result of facilitated diffusion do not achieve the same degree of storage in the developing fetus. Thus, the premature infant who has decreased stores and who may have impaired oral absorption initially may become deficient in a fat-soluble vitamin (A, D, E, K) during the first 4 to 6 weeks of life. Oral or possibly parenteral supplementation following birth, however, would seem more appropriate than subtoxic doses administered to the mother prenatally.