Vitamin D during pregnancy improves children’s bone health for years to come, study shows

A recent follow-up study to the MAVIDOS study confirmed that vitamin D supplementation during pregnancy improves bone mineral density in offspring, and these benefits persist up to seven years of age.

Test: Vitamin D supplementation during pregnancy and childhood bone mineral density in offspring. Follow-up of a randomized controlled trial. Photo source: April / Shutterstock.com

Previously, the MAVIDOS study found that vitamin D supplementation during pregnancy significantly improved bone mineral density (BMD) in offspring, measured four years later. In a recent study published in American Journal of Clinical NutritionScientists are investigating the durability of this BMD improvement later in childhood.

What is the MAVIDOS study?

The MAVIDOS study was a randomised controlled trial (RCT) that assessed the effect of vitamin D supplementation during pregnancy in the UK. All participants in the study were between 11 and 14 weeks of pregnancy and received 1000 IU vitamin D/day until delivery.

A total of 965 individuals participated in the study, of whom 723 were born at term. Of these term children, 477 underwent dual-energy X-ray absorptiometry (DXA) scans, which allowed for assessment of BMD at age four. At the second time point, at age six to seven, 447 children underwent a second DXA scan.

Children who completed the second visit were more likely to be born to nonsmoking, older mothers with higher education. These children also had a longer duration of breast milk consumption, with a compact raise in the percentage of children taking vitamin D supplements since the initial assessment visit.

Better bone healing results

Whole-body headless (WBLH) DXA scans were used to measure BMD and bone mineral density (BMAD). Both WBLH BMD and BMAD were higher in the vitamin D group than in the placebo group at six to seven years of age.

Even after taking into account gender, height, weight, duration of breastfeeding and vitamin D supplementation at age six to seven years, children whose mothers took vitamin D supplements during pregnancy had higher WBLH, BMD and BMAD measurements.

For the subgroup of children who had DXA scans at birth and at both assessment points, similar increases were observed at both time points for WBLH bone scores. There was also a trend toward increased lumbar spine BMAD at six to seven years of age.

The primary objective of the MAVIDOS study was to examine improvements in BMC at birth, which did not show a difference with supplementation. However, infants born in the winter months showed higher bone mineral content (BMC) than placebo.

How do these results compare to other studies?

The study results are consistent with those of the Copenhagen Prospective Study of Asthma in Children (COPSAC)₂₀₁₀) study. However, the Bangladesh study did not find such improvements. Although underlying health conditions such as malnutrition and infections may contribute to these conflicting findings, additional research is needed to explain these differences.

An Australian observational study showed similar positive results in offspring at age 20 years, following the administration of a vitamin D supplement to the mother at 18 weeks of pregnancy.

How does maternal vitamin D supplementation support bone density in children?

Vitamin D supplementation during pregnancy does not raise calcium availability to the developing fetus, despite higher fetal vitamin D levels in the first few months of life, which may aid calcium absorption. Higher antirickets activity in breast milk may also contribute to higher bone mineralization in the child.

Epigenetic mechanisms may also be involved in the effects of vitamin D supplementation on bone outcomes in later childhood, but not at birth. For example, vitamin D may stimulate the bone response to mechanical loading when a child begins to move independently. Alternatively, higher levels of vitamin D in early childhood promote spine growth at a time when it occurs rapidly, thereby improving its mineralization in early rather than later childhood.

Conclusions

The study results confirm that the positive effects associated with vitamin D supplementation during pregnancy persist beyond the fourth year of life and into later childhood. However, validation and extension of these results are warranted to guide recommendations for vitamin D supplementation during pregnancy at a dose of 1000 IU/day.

The observed raise in BMD in childhood is expected to reduce the risk of fracture, as supported by one retrospective analysis of a Danish study. Further research is needed to determine whether this raise in BMC and BMD persists as children transition into adulthood. These effects would be clinically significant in reducing the risk of fragility fracture.