Results show vitamin D supplementation during pregnancy improves maternal and infant 25(OH)D concentrations and may play a role in maternal insulin resistance and fetal growth. Literature search was performed using PubMed Database of the National Library of Medicine, with date limits from January 2015 to November 2020. We used the keywords: Vitamin D, pregnancy, vitamin D supplementation, hypovitaminosis D, preeclampsia, gestational diabetes, preterm birth, and other related terms. The studies of interest included original papers and review articles on the influence of vitamin D deficiency in pregnancy and the impact of vitamin D supplementation on the maternal outcomes. The published Cochrane review on vitamin D supplementation studies reported that women who receive vitamin D supplementation had lower risk of preeclampsia but with only borderline significance (RR 0.52, CI 0.25–1.05), whereas combined vitamin D and calcium supplementation significantly reduces the risk of preeclampsia. The overall level of evidence is high for vitamin D supplementation playing no role in the prevention of gestational diabetes. Although analysis of the recent observational studies suggests that vitamin D deficiency can increase the risk of C section, there is a need for investigators to conduct RCT to study the impact of vitamin D supplementation on C-section rates. Maternal vitamin D status closest to the delivery was most significantly associated with preterm birth, thereby proposing that later intervention could be used as a rescue treatment to decrease the risk of preterm deliveries. Though the level of evidence is moderate, our analysis shows no significant association between vitamin D and preterm deliveries. Many studies have been designed to investigate an association between postpartum depression and vitamin D. To determine the benefits of vitamin D supplementation in pregnancy would require further evaluation through large, multicenter double-blind randomized controlled clinical trials, with a focus on specific adverse pregnancy outcomes.
The impact of vitamin D deficiency on maternal outcomes in pregnancy
