Vitamin D deficiency is common in pregnant women, causing harm to maternal well-being, fetal development and the child’s long term skeletal health. Although a standardised vitamin D supplement is recommended during pregnancy, many factors can affect how much such supplements translate into a raised maternal vitamin D level.

Moon et al. studied 829 pregnant women from 14 weeks of gestation. Half were given a dose of 1000IU cholecalciferol per day, while the remainder received a placebo. The supplement had a significant positive effect in raising maternal vitamin D. However, in the group given vitamin D, factors associated with a lower level of maternal vitamin D at 34 weeks included higher pregnancy weight gain, lower compliance in taking the supplement, lower early pregnancy vitamin D levels and giving birth in the winter (as opposed to the summer).

The findings suggest that the exact levels of vitamin D supplementation recommended for pregnant women should be tailored to an individual’s circumstances, such as anticipated season of delivery.

Read the full article in Journal of Clinical Endocrinology & Metabolism doi:10.1210/jc.2016-2869