Pregnancy vitamin D supplementation and bone mineral density of the mother: a post hoc analysis of the MAVIDOS randomised placebo-controlled trial.

UNLABELLED: The effect of pregnancy vitamin D supplementation on bone mineral density (BMD) in the mother immediately after delivery and at 4 years after delivery was assessed in a randomised placebo-controlled trial. The mothers' BMD did not differ between the two intervention groups.

PURPOSE: Vitamin D supplementation during pregnancy has positive effects on the offspring's bone development and bone mineral density (BMD) in childhood, but there are limited data on the effects on the mother's skeleton. We assessed this in a post hoc follow-up of a randomised trial.

METHODS

MAVIDOS was a randomised placebo-controlled trial of 1000 IU/day cholecalciferol from 14 to 17 weeks gestation until delivery. Participants were invited to have a dual-energy X-ray absorptiometry (DXA) scan of the whole body, lumbar spine (LS) and left hip within 2 weeks after delivery and again 4 years after delivery. BMD was compared between the cholecalciferol and placebo groups; in women with DXA at both time points, the effect of cholecalciferol was assessed using mixed effects modelling to account for repeated measures.

RESULTS

Four hundred one and 443 participants had a DXA within 2 weeks after delivery and at a mean of 4.1 years after delivery, respectively. Cholecalciferol supplementation increased serum 25-hydroxyvitamin D status in late pregnancy compared to placebo. BMD at all sites was similar between the two randomisation groups at both time points (p > 0.05 for all). Two hundred sixty-three participants had a DXA at both birth and 4 years. BMD increased between 1 and 6% depending on the site from within 2 weeks to 4 years after delivery. This was similar between randomisation groups. The pregnancy cholecalciferol had no effect on BMD at 4 years in repeated measures modelling.

CONCLUSIONS

Despite previously demonstrated benefits for the offspring skeleton in this trial, maternal BMD did not differ in the short or medium term in women randomised to 1000 IU/day vitamin D or placebo.