Vitamin D supplementation during pregnancy and maternal and neonatal outcomes: results from a quantitative umbrella meta-analysis

This umbrella meta-analysis aimed to examine the effect of prenatal vitamin D supplementation on maternal and neonatal outcomes. Scopus and PubMed were searched up to September 2024 to include relevant studies. The outcomes included gestational diabetes mellitus (GDM), preeclampsia, cesarean section, preterm delivery (PTD), low birth weight (LBW), small for gestational age (SGA), stillbirth, neonatal mortality, birth weight, birth length, and head circumference at birth. Standardized mean difference (SMD) and relative risk (RR) with their 95% confidence intervals (CI) were used as effect sizes to pool the data using a random effects model. Thirty-five studies with 188,370 participants were included. Vitamin D supplementation lowered the risk of GDM (RR = 0.68, 95%CI: 0.53 to 0.88), preeclampsia (RR = 0.62, 95%CI: 0.56 to 0.69), PTD (RR = 0.77, 95%CI: 0.65 to 0.90), LBW (RR = 0.67, 95%CI: 0.54 to 0.84), SGA (RR = 0.73, 95%CI: 0.63 to 0.85), stillbirth (RR = 0.77, 95%CI: 0.62 to 0.95), and neonatal mortality (RR = 0.58, 95%CI: 0.40 to 0.84), while also enhanced birth weight (SMD = 75.68, 95%CI: 48.99 to 102.36), birth length (SMD = 0.25, 95%CI: 0.18 to 0.33), and head circumference (SMD = 0.15, 95%CI: 0.06 to 0.23). These effects were observed with lower doses of vitamin D ((< 50,000 IU/week), shorter intervention periods (< 14 weeks), and among older participants ((≥ 27 years). Moreover, vitamin D supplementation was linked to the reduced risk of cesarean deliveries in some subgroups. Prenatal vitamin D supplementation may be associated with a lower risk of certain adverse maternal and neonatal outcomes and may improve birth anthropometric measurements.