Association of vitamin D level and maternal gut microbiome during pregnancy: Findings from a randomized controlled trial of antenatal vitamin D supplementation

Summary

This randomised controlled trial analysed gut microbiome and vitamin D data from pregnant women in the VDAART study to investigate associations between maternal vitamin D status and microbiome composition. Whilst baseline vitamin D level was associated with microbiome composition, vitamin D supplementation during pregnancy did not shift the overall microbiome structure. The genus Desulfovibrio, a sulphate-reducing bacterium implicated in inflammatory disorders, was enriched in women whose vitamin D levels did not increase substantially from early to late pregnancy, suggesting potential protective effects of adequate vitamin D against pathogenic bacterial growth.

Regional applicability

The study was conducted in the United States as part of a large trial. Findings on vitamin D–microbiome associations may be relevant to United Kingdom maternal and child health policy, particularly given variable vitamin D status in UK pregnant women; however, microbiome composition may differ by geography and dietary patterns, warranting validation in UK cohorts.

Key measures

Vitamin D levels (blood samples, early and late pregnancy); gut microbiome composition (stool samples, late pregnancy); alpha diversity measures; beta diversity distances; differential taxa abundance (ANCOM-BS and Maaslin2 algorithms); genus-level abundance (Desulfovibrio)

Outcomes reported

The study examined associations between maternal vitamin D status (measured in early and late pregnancy) and gut microbiome composition (alpha and beta diversity, and differential taxa abundance) in pregnant women receiving vitamin D supplementation or placebo. It identified enrichment of Desulfovibrio genus in women without substantial vitamin D increase between trimesters.

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