The main focus of this systematic review and meta-analysis was to explore the link between maternal concentrations of vitamin D (25-hydroxyvitamin D) and the occurrence of preeclampsia (one of the most common causes of maternal mortality worldwide). Furthermore, the effects of supplementing vitamin D on the incidence of preeclampsia were also analyzed.

A comprehensive investigation was conducted utilizing the Medline database. Thirty-four papers, ten randomized controlled trials and twenty-four observational studies were included. The studies included in the analysis investigated the connection between deficiency in 25-hydroxyvitamin D and preeclampsia, as well as the influence of supplementing 25-hydroxyvitamin D on the occurrence of preeclampsia. The outcomes were presented through a random-effects meta-analysis and the Mantel-Haenszel odds ratio. For the assessment, a p-value of <0.05 was deemed significant.

Supplementing with 25-hydroxyvitamin D was found to be significantly linked to a reduced risk of preeclampsia in pregnant women (Odds Ratio [OR]: 0.50; 95% Confidence Interval [CI]: 0.40-0.63; p = 0.00001). Conversely, 25-hydroxyvitamin D deficiency was substantially associated with an elevated risk of preeclampsia (OR: 4.30; 95% CI: 2.57-7.18; p < 0.00001, OR: 1.71; 95% CI: 1.27-2.32; p = 0.0005, OR 1.61; 95% CI: 1.21-2.16; p = 0.001).

The findings established a vital connection between the heightened risk of preeclampsia and low maternal levels of 25-hydroxyvitamin D. Furthermore, vitamin D use substantially diminished the occurrence of preeclampsia. Hence, this supplementation could be considered as a potential intervention strategy in preventing preeclampsia.