Do vitamin D levels in mothers have an effect on their child’s bone health?

According to a new study from the UK there is no evidence that women’s blood vitamin D concentrations during pregnancy are associated with the offspring’s total body or spinal bone mineral concentrations. However, experts recommend vitamin D supplementation during pregnancy to support both maternal and fetal bone health.

The observational study measured 25-hydroxyvitamin D blood levels of 3960 pregnant women in all tri-mesters (1). At an average age of nine years and 11 months, their children’s bone mineral content (BMC) was assessed by dual-energy X-ray absorptiometry. The study results showed no significant association between the mothers’ vitamin D levels and their children’s BMC. The vitamin D levels of the women were on average lowest during their first trimester, and then increased as the pregnancy progressed; as expected, levels were higher when measured during summer months and lower when measured during winter months. Although non-white mothers and those who smoked during pregnancy tended to have lower vitamin D levels overall, this appeared to have no effect on their children’s bone health.

The researchers commented that health guidelines may be overstating the importance of vitamin D supplementation in pregnancy, saying there is no strong evidence that pregnant women should receive vitamin D supplementation to prevent low BMC in their offspring. However, there could be other possible beneficial effects of vitamin D in pregnant women, they said.

Previous studies on maternal vitamin D status and offspring’s bone health have produced inconsistent results. Experts recommend routine vitamin D supplementataion for pregnant women who are at increased risk of deficiency. Currently, the American College of Obstetrics and Gynecology and the Institute of Medicine recommend 600 IU of daily vitamin D supplementation during pregnancy to support maternal and fetal bone metabolism (2). Vitamin D supplementation has been suggested to prevent pre-eclampsia, gestational diabetes, impaired glucose tolerance, gestational hypertension and even death among mothers, and preterm birth, infection or death of newborns.

1. Lawlor D. A. et al. Association of maternal vitamin D status during pregnancy with bone-mineral content in offspring: a prospective cohort study. The Lancet. Published online March 2013.
2. American College of Obstetrics and Gynecology. Vitamin D - Screening and Supplementation During Pregnancy. Committee Opinion. No. 495; July 2011.