Vitamin D during pregnancy doesn't aid child's bones, study shows Official health guidelines could be overstating the importance of taking Vitamin D supplements during pregnancy, a report has shown. A study of nearly 4,000 pairs of mothers and their children published in health journal The Lancet showed that maternal vitamin D levels are not associated with the child's bone health later in life. Professor Debbie Lawlor of the University of Bristol said: "We believe that there is no strong evidence that pregnant women should receive vitamin D supplementation to prevent low BMC (bone mineral content) in their offspring, although we cannot comment on other possible effects of vitamin D in pregnant women." The NHS recommends that pregnant women, as well as women who breastfeed, should take a 10 micrograms supplement of vitamin D each day. A lack of Vitamin D can cause bones to soften, potentially leading to rickets.