Vitamin D metabolism in preterm infants.

Perinatal metabolism of vitamin D was studied in premature babies with the aim of: (1) reporting the relationship between the pregnant mother and her preterm infant and the metabolism of vitamin D during the first weeks of life, and (2) assessing the effect of vitamin D metabolites on phosphorus calcium and magnesium intestinal absorption. There was only a positive correlation between plasma cord calcium and 25-hydroxyvitamin D levels and the mother's plasma levels at birth. During the hypocalcemic episode observed during the first week of life, vitamin D activation did occur, but later on rickets or osteomalacia cannot be due to the low levels of vitamin D metabolites in the preterm receiving an adequate dose of vitamin D (1,000-1,200 IU of D2). Calcitriol, the major metabolite of vitamin D, is acting on the intestine and promotes calcium absorption even in very tiny prematures. The pathogenesis of hypomineralization in the preterm infant is due to the low intake of calcium or phosphorus and/or poor absorption of calcium in the case of vitamin D deficiency.