Pregnant women may help their babies by taking vitamin D supplements during the winter, researchers report today.
But at other times of the year there is little evidence the supplements can help a child’s bone health, according to the UK-based study.
Pregnant women in the UK are currently encouraged to take 10µg of vitamin D per day, with the aim of improving the foetus’s bone development. There is a lack of evidence from randomised trials, the researchers say.
The impact of vitamin D supplementation was examined by Professor Cyrus Cooper of Southampton University, UK, and colleagues. They recruited 1,134 women in Southampton, Oxford, and Sheffield between 2008 and 2014. All had had low to normal vitamin D levels. Participants were given either a 25µg vitamin D capsule daily or placebo, from 14 to 17 weeks’ gestation until the birth.
No significant differences were seen in overall bone mass scans between the two groups.
But further investigation showed there may have been a benefit for babies born during winter months. The mothers who gave birth at this time of year also showed drops in their own vitamin D if they were on placebo, but a rise in their vitamin D if they were taking the supplement.
"This suggests that vitamin D supplementation may counteract the drop in the body’s normal levels of vitamin D caused by lack of sunlight when late pregnancy occurs in the winter months," state the authors in today’s (2 March) Lancet Diabetes & Endocrinology.
Co-author Professor Nicholas Harvey commented: "This trial has given us the first evidence that supplementing mothers with vitamin D during pregnancy counteracts the seasonal drop in maternal vitamin D levels and may help to ensure good bone development in these winter births."
Cooper, C. et al. Maternal gestational vitamin D supplementation and offspring bone health (MAVIDOS): a multicentre, double-blind, randomised placebo-controlled trial. Lancet Diabetes & Endocrinology 2 March 2016 doi: 10.1016/S2213-8587(16)00044-9 [abstract]
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