Taking vitamin D supplements during pregnancy was only beneficial for babies born during the winter time, a UK study has found.
The study of over 1,000 expectant mums showed that overall, taking a daily vitamin D pill – as currently recommended for all pregnant women in national guidelines – made no difference to newborn babies’ bone strength.
However, babies born during winter months did seem to benefit – among these, babies born to mothers who took vitamin D had greater bone mass than those whose mothers took a placebo.
Authors of the study – published in the Lancet Diabetes and Endocrinology – said this suggested the supplements help to counteract low maternal vitamin D levels due to lack of sunlight during the late stages of pregnancy.
They said they still supported the current blanket approach to vitamin D supplementation in pregnancy, which their study had shown was ‘safe’ and ‘sufficient to ensure that most pregnant women are vitamin D replete’.
But Professor Ian Reid from the University of Auckland, said in a linked commentary that ‘in pregnancy and other contexts, we should be moving to targeted supplementation with vitamin D… and away from mass medication, which is without proved benefit’.
The Department of Health currently recommends all pregnant women take 10 micrograms of a vitamin D supplement daily.
The Royal College of Obestricians (RCOG) said that more research was needed to determine whether women at low-risk of vitamin D deficiency could stop taking supplements – and stressed women from high-risk groups must get their ‘required dose’.
RCOG spokesperson Dr Daghni Rajasingam said: ‘Women more at risk of having low vitamin D levels include those of south Asian, black African, black Caribbean, or Middle Eastern origin, women who have limited exposure to sunlight, obese women and those who eat a diet particularly low in vitamin D. It is particularly important these women get their required dose’.
Dr Rajasingam added: ‘In light of this study, further research on the effectiveness of vitamin D supplementation on women at low-risk of deficiency would be beneficial.’
Lancet 2016; available online 1 March