[Administration of a single dose of 100,000 U.I. of vitamin D3 in the pregnant woman in winter. The effect on blood calcium level of the newborn infant].

Serum levels of 25-hydroxyvitamin D [25-(OH)D], calcium, phosphate and alkaline phosphatase activity were measured between December and July in 110 pregnant women during the last trimester of pregnancy, and in their infants on the fifth day of life. This study showed a fall, during spring, below 6 ng/ml, of the maternal 25-(OH)D concentration at the time of delivery, and a fall of the 25-(OH)D and calcium concentrations in newborns. The existence of a positive correlation between calcium and 25-(OH)D levels in the newborns suggests that the low calcium concentrations found in the infants born in spring is related to a vitamin D deficiency of the infant and therefore of the mother. The administration of a single low dose of vitamin D3 (100,000 I.U.) on the sixth or seventh month of pregnancy allowed to prevent the seasonal fall in serum calcium and 25-(OH)D concentrations. This dosage appears therefore to be sufficient to reduce the risk of vitamin D deficiency of the newborn and the occurrence of neonatal hypocalcemia.