medwireNews: UK researchers have raised questions about recommendations for vitamin D supplementation after finding that maternal vitamin D levels during pregnancy are not linked to the child's future bone health.
The study of 3960 mothers, of whom 34% had insufficient or deficient 25-hydroxyvitamin D (25(OH)D) concentrations (<50 nmol/L), failed to find an association between median maternal 25(OH)D concentrations in any trimester and the child's bone mineral content (BMC) at a mean age of 9.9 years.
And, the mean offspring BMC in those born to 25(OH)D-insufficient and -deficient mothers was similar to that in those born to mothers with sufficient levels.
The association has only previously been examined in a handful of small studies, the authors explain in The Lancet. Nevertheless, since 2008, the UK guidance body NICE has recommended that all pregnant and breastfeeding women take a 10 µg vitamin D supplement daily. The Canadian Paediatric Society also recommends that pregnant and breastfeeding women take five times this daily amount. However, the American College of Obstetricians and Gynecologists has refused to make recommendations due to lack of evidence.
Debbie Lawlor (University of Bristol, UK) and colleagues believe "that there is no strong evidence that pregnant women should receive vitamin D supplementation to prevent low BMC in their offspring."
However, in an accompanying commentary, Philip Steer (Imperial College London, UK) said that there was still reason to recommend supplementation for certain women during pregnancy to reduce the risk of rickets.
"The safest approach is probably routinely to supplement pregnant women at greatest risk, as defined by the NICE guidelines: women of south Asian, black African, black Caribbean, or Middle Eastern origin, women who have limited exposure to sunlight …, women who eat a diet particularly low in vitamin D …, and women with a body-mass index higher than 30 kg/m² before pregnancy," Steer advised.
By Kirsty Oswald, medwireNews Reporter