Maternal vitamin D deficiency: Fetal and neonatal implications.

Recent research efforts have focused on the roles that vitamin D may play in skeletal and non-skeletal health during pregnancy, lactation, and fetal or neonatal development. Animal and clinical studies have shown that the mother provides calcium to the fetus and neonate without requiring vitamin D, calcitriol, or the vitamin D receptor. Consequently, the blood calcium, calciotropic hormones, and skeleton are normal at birth despite severe vitamin D deficiency or genetic deletion of calcitriol or vitamin D receptor. After birth intestinal calcium absorption becomes dependent upon calcitriol, and this is when hypocalcemia and rickets can begin to develop. Breastfed infants are at especially high risk of vitamin D deficiency due to poor penetrance of vitamin D metabolites into milk. To maximize skeletal and non-skeletal health, vitamin D dosing recommendations should ensure that the baby is born vitamin D sufficient and maintained that way during infancy and beyond.