Vitamin D supplementation in pregnant women improves bone mass in offspring

Children born to mothers receiving vitamin D supplementation during pregnancy are more likely to have a higher bone mass if born during the winter months, according to recent study findings presented at The American Society for Bone and Mineral Research Annual Meeting.

In a randomized, double-blind, placebo-controlled study testing whether the offspring of mothers supplemented with vitamin D have a higher bone mass than the offspring of mothers who were not supplemented, the researchers also found that mothers in the supplement group did not experience a seasonal decline in vitamin D levels.

Cyrus Cooper, OBE, MA, DM, FRCP, FFPH, FMedSci, director of the MRC life course epidemiology unit at University of Southampton, and colleagues analyzed data from 954 pregnant women participating in the MAVIDOS study in the U.K. Women underwent an ultrasound and vitamin D measurements at 12 weeks gestation before being randomly assigned to either 1,000 IU oral vitamin D (n = 477) or matching placebo (n = 477) at 14 weeks gestation. Vitamin D levels were measured again at 14 weeks and 34 weeks gestation. Within 2 weeks of birth, infants underwent whole-body DXA scans to measure bone mineral content; DXA information was available for 665 infants.

Cyrus Cooper

Researchers found that whole body bone mineral content was greater for infants born to mothers in the supplement group, though the measurements were not significant (61.6 g vs. 60.5 g).

“However, in a pre-specified analysis, there was an interaction between treatment allocation and season of birth (P = .04), such that infants born in winter months [December to February] to mothers randomized to [vitamin D] had greater [bone mineral content] than infants of mothers randomized to placebo, a difference of 0.5 SD.”

Researchers found that infants born in the winter months had mean bone mineral content measurements of 63 g, vs. 57.5 g in the placebo group (P = .004). Similar patterns were seen in bone area and bone mineral density measurements.

In the placebo group, vitamin D levels declined between 14 and 34 weeks gestation for women who delivered in the winter or spring, but increased in women who delivered in summer or autumn.

“These seasonal differences were entirely removed by vitamin D supplementation, with 25(OH)D rising from 14 to 34 weeks irrespective of season of birth,” the researchers wrote.

“The findings show a beneficial effect of supplements only for births during winter, and this is because the supplements eliminated the marked decline in maternal vitamin D levels between summer and winter for that subset of pregnancies,” Cooper told Endocrine Today. “They will inform public health policy on vitamin D supplementation during pregnancy (suggesting that a minimum of 400IU daily is necessary for all, but that 1000IU daily is required for mothers at higher risk of insufficiency).” – by Regina Schaffer

Reference:

Cooper C, et al. FR0052. Presented at: The American Society for Bone and Mineral Research Annual Meeting; Oct. 9-12, 2015; Seattle.

Disclosure: Cooper reports receiving previous speaking fees and honoraria from Amgen, Lilly, GlaxoSmithKline, Servier. Shire, Danone and MSD.