# A systematic review and meta analysis on the effect of vitamin D in preeclampsia and gestational diabetes mellitus in pregnancy

## TL;DR

This study finds that vitamin D supplementation during pregnancy may reduce risks of preeclampsia and gestational diabetes, especially in the first trimester.

## Contribution

The study provides a meta-analysis showing vitamin D supplementation reduces preeclampsia and gestational diabetes risks, particularly in vitamin D-deficient women.

## Key findings

- Vitamin D supplementation reduced preeclampsia risk by 42% and GDM by 45% in RCTs.
- Vitamin D deficiency was linked to increased GDM risk but not preeclampsia in cohort studies.
- Supplementation was most effective in reducing recurrent preeclampsia in vitamin D-deficient women.

## Abstract

Preeclampsia and gestational diabetes mellitus (GDM) are significant contributors to maternal and neonatal morbidity and mortality, particularly in low- and middle-income countries. Vitamin D might play a role in the pregnancy complication prevention. However, findings across studies remain inconsistent. In this review, we aimed to evaluate vitamin D deficiency effect on preeclampsia and GDM risks, and the effect of vitamin D supplementation during pregnancy in reducing preeclampsia and GDM incidences.

We followed the PRISMA guidelines and registered the protocol with PROSPERO (CRD42024609276). Database PubMed, Scopus, and EBSCO-Medline were used to search cohort and randomized controlled trial (RCT) studies published between 1993 and 2025. Two reviewers independently assessed the article quality with the Joanna Briggs Institute checklists and extracted data. Meta-analyses were performed using RevMan 5.4. The results were reported in pooled odds ratios (OR) or standardized mean differences (SMD) with 95% confidence intervals.

A total of 52,372 participants from 24 studies were included in this review. Vitamin D supplementation appeared to reduce the preeclampsia risk by 42% (OR = 0.58; 95%CI: 0.43–0.78; I2 = 45%) and GDM by 45% (OR = 0.55; 95%CI: 0.36–0.87; I2 = 0%) in RCTs. Vitamin D supplementation is most effective in reducing the risk of recurrent preeclampsia in women with vitamin D deficiency. In cohort studies, vitamin D deficiency was associated with a higher risk of GDM (OR = 1.29; 95% CI: 1.16 to 1.43; I² = 7%), but was not significantly associated with preeclampsia (OR = 1.67; 95% CI: 0.92 to 3.01; I² = 85%).

Vitamin D supplementation in pregnancy, especially in the first trimester, decreased preeclampsia and GDM risks, while vitamin D deficiency in pregnancy increased GDM risk but not preeclampsia. These findings support the potential benefit of vitamin D supplementation in the routine antenatal care to improve pregnancy outcomes.