[Vitamin D and pregnancy].

During pregnancy maternal serum concentrations of 25 hydroxyvitamin D correlate with dietary vitamin D intake. Maternal serum concentrations of 1.25-dihydroxyvitamin D the hormonal circulating and active form of vitamin D are elevated, during pregnancy. 1.25-dihydoxyvitamin D is synthesized mainly by the décidual cells of the placenta and allows for increased calcium absorption. The fetus is entirely dependent on the mother for its supply of 25 (OH) D which is believed to cross easily the placenta. Vitamin D deficiency during pregnancy affects the fetus and the newborn. Birth weight is decreased, bone mineralization is impaired and neonatal hypocalcemia is frequent. In countries where dairy products are not routinely supplemented in vitamin D maternal vitamin D supplementation during pregnancy is necessary.