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 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: Protocol registered in PROSPERO (CRD42022368003). Searches were conducted in PubMed, Embase, and Cochrane Library from inception to October 2, 2023. Two reviewers independently selected studies and extracted outcomes; methodological quality was assessed using AMSTAR 2. Results: Sixteen eligible systematic reviews and meta-analyses (n=250,569 women across included primary studies) were identified. Vitamin D deficiency in pregnancy was associated with increased risks of preterm birth, small-for-gestational-age/low birth weight, recurrent miscarriage, bacterial vaginosis, and gestational diabetes mellitus. Supplementation increased birth length/weight in some analyses and reduced risks of maternal pre-eclampsia and miscarriage, fetal or neonatal mortality, and childhood ADHD and ASD; in women with gestational diabetes, supplementation reduced maternal and neonatal complications. Conclusion: Monitor vitamin D status in pregnancy, especially in high-risk women; supplementation >400 IU/day is suggested during pregnancy to prevent certain adverse outcomes.