Vitamin D Supplements in Pregnancy: What’s the Latest Evidence?

Vitamin D Supplements in Pregnancy: What’s the Latest Evidence?
Recent evidence suggests that women supplementing Vitamin D while pregnant, might have some health benefits. Shutterstock
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What we Already Know

Vitamin D forms from sunlight on the skin and is used by the body to absorb calcium, needed for healthy bones and teeth. Up to half of all pregnant women in the UK are deficient, which is more common in winter than in summer. Vitamin D deficiency disproportionately affects black and minority ethnic groups, those who cover their skin, those who are overweight and those with chronic illness, and particular care should be taken to advise these women (National Institute for Health and Care Excellence, 2019).
Pregnant women who are deficient (blood serum level <50nm) are more likely to have pregnancy complications including pre-eclampsia, diabetes, preterm birth and small babies. Babies born deficient may have affected bone growth or in severe cases rickets (flexible bones). Deficiency has also been linked with the development of childhood allergy (European Food Safety Authority, 2016; Royal College of Obstetricians & Gynaecologists, 2014).

An Evidence Gap

Whilst the Royal College of Obstetricians and Gynaecologists (RCOG) supports supplementing pregnant women with vitamin D (Royal College of Obstetricians & Gynaecologists, 2014), until now there has been a lack of evidence confirming the benefits and harms of this. In practice, it has been confusing what to advise women, should they be given a low dose supplement, a high-dose supplement, or should they be tested for deficiency and treated if deficient in this important nutrient?