Effects of vitamin D in pregnancy on maternal and offspring health-related outcomes: An umbrella review of systematic review and meta-analyses.

Background: Vitamin D deficiency has been linked with several adverse maternal and fetal outcomes.

Objective: To summarize systematic reviews and meta-analyses evaluating the effects of vitamin D deficiency and of vitamin D supplementation in pregnancy on maternal and offspring health-related outcomes.

Methods: Prior to conducting this umbrella review, we registered the protocol in PROSPERO (CRD42022368003). We conducted searches in PubMed, Embase, and Cochrane Library for systematic reviews and meta-analyses on vitamin D in pregnancy, from database inception to October 2, 2023. All outcomes related to vitamin D in pregnancy obtained from the systematic reviews and meta-analyses were extracted.

Data extraction: Two reviewers independently chose studies and collected information on health outcomes. The quality of the included articles' methodology was assessed using AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews-2).

Results: We identified 16 eligible systematic reviews and meta-analyses, which included 250,569 women. Our results demonstrated that vitamin D deficiency in pregnancy is associated with increased risk of preterm birth, small-for gestational age/low birth weight infants, recurrent miscarriage, bacterial vaginosis and gestational diabetes mellitus. Vitamin D supplementation in pregnancy increases birth weight, and reduces the risk of maternal pre-eclampsia, miscarriage, and vitamin D deficiency, fetal or neonatal mortality, as well as attention-deficit hyperactivity disorder, and autism spectrum disorder in childhood. In women with gestational diabetes mellitus, vitamin D supplementation in pregnancy can reduce the risk of maternal hyperbilirubinemia, polyhydramnios, macrosomia, fetal distress, and neonatal hospitalization.

Conclusion: Due to the association with adverse maternal and offspring health outcomes, we recommend the vitamin D status in pregnancy should be monitored, particularly in women at high risk of vitamin D deficiency. It is suggested that pregnant women take a dose of >400 IU/day of vitamin D supplementation during pregnancy to prevent certain adverse outcomes.