Vitamin D and preeclampsia: A systematic review and meta-analysis

Objectives: Preeclampsia is one of the most frequent pregnancy disorders, with a global incidence of 2%-8%. Serum 25-hydroxyvitamin D is an essential mineral for human health; some studies suggest link between 25-hydroxyvitamin D deficiency and preeclampsia, while others offer contradictory findings. Thus, the goal of this study is to evaluate the relationships between maternal 25- hydroxyvitamin D concentrations and the risk of preeclampsia. In addition to this, our study also evaluates the effects of 25- hydroxyvitamin D supplementation on the incidence of preeclampsia. Therefore, assessing 25- hydroxyvitamin D's potential as a possible intervention to lower the risk of preeclampsia.Methods: The Medline database was queried from inception until July 2021 for randomized controlled trials and observational studies without any restrictions. The studies assessing the association between 25-hydroxyvitamin D deficiency and preeclampsia and the impact of 25-hydroxyvitamin D supplementation on the incidence of preeclampsia were incorporated. The results were reported using a random-effects meta-analysis and the Mantel-Haenszel odds ratio. A p-value of <0.05 was considered significant for the analysis.Results: This analysis includes 34 papers, including 10 randomized controlled trials and 24 observational studies. According to our pooled analysis, 25-hydroxyvitamin D supplementation was significantly associated with a lower risk of preeclampsia in pregnant women (OR: 0.50; 95% CI: 0.40-0.63; p = 0.00001), while 25-hydroxyvitamin D deficiency was significantly associated with an increased risk of preeclampsia (OR: 4.30; 95 % CI: 2.57-7.18; p < 0.00001, OR: 1.71; 95 % Cl: 1.27-2.32; p = 0.0005, OR 1.61; 95 % Cl: 1.21-2.16; p = 0.001).Conclusion: Results suggest that 25-hydroxyvitamin D has a significant relationship with preeclampsia as confirmed by the findings that low maternal 25-hydroxyvitamin D concentrations cause increased risk of preeclampsia while 25-hydroxyvitamin D supplementation reduces the incidence of preeclampsia. Our findings indicate that 25-hydroxyvitamin D supplementation can be used as a possible intervention strategy in preventing one of the most common causes of maternal mortality around the world, preeclampsia.