Vitamin D Supplementation in Pregnancy Might Benefit Infants Born in Winter

By Kelly Young

Edited by David G. Fairchild, MD, MPH, and Lorenzo Di Francesco, MD, FACP, FHM

Vitamin D supplementation during pregnancy is not associated with improved bone mineral content in offspring overall, but it may offer some benefit to children born in winter months, suggests a Lancet Diabetes and Endocrinology study.

Roughly 1100 U.K. pregnant women with baseline 25(OH)D concentrations between 25 and 100 nmol/L were randomized to receive either daily oral cholecalciferol (1000 IU) or placebo beginning at 14–17 weeks' gestation.

The primary outcome — whole-body bone mineral content of the newborn — did not differ significantly between the groups. However, among infants born in winter months, the cholecalciferol group did have significantly higher bone mineral content than the placebo group. Maternal 25(OH)D declined from 14 to 34 weeks' gestation in women who delivered in winter and spring and took placebo — but not among those who took cholecalciferol.

A commentator writes: "In pregnancy and other contexts, we should be moving to targeted supplementation with vitamin D in individuals likely to have concentrations of lower than 25–30 nmol/L, and away from mass medication, which is without proved benefit."