Abstract
BACKGROUND: Vitamin D is critical for immune regulation and respiratory health, yet its supplementation during pregnancy shows inconsistent results in preventing respiratory and allergy-related outcomes in children. This systematic review and meta-analysis aim to evaluate the impact of maternal vitamin D supplementation on respiratory tract infections (RTI), asthma, wheezing, eczema, and allergy in offspring. METHODS: A comprehensive search was performed in PubMed, Embase, Web of Science, Cochrane Library up to December 2024. We included randomized controlled trials (RCTs) examining the effects of prenatal vitamin D supplementation on respiratory and allergy-related outcomes in children. The GRADE approach was applied to assess the quality of evidence, and the Cochrane risk-of-bias tool was used to evaluate study quality. RESULTS: Seven RCTs were included (3958 mother-infant pairs). Prenatal vitamin D supplementation did not significantly reduce RTI in children compared to controls (RR = 1.018, 95% CI: 0.965 to 1.074, p = 0.514). Similarly, no significant effects were observed for asthma (RR = 0.395, 95% CI: 0.670 to 1.308, p = 0.699), wheezing (RR = 0.824, 95% CI: 0.826 to 1.089, p = 0.174), eczema (RR = 0.954, 95% CI: 0.826 to 1.102, p = 0.522), allergic conditions (RR = 0.938, 95% CI: 0.841 to 1.047, p = 0.255), or IgE positivity (RR = 0.942, 95% CI: 0.736 to 1.207, p = 0.639). Subgroup analyses showed no significant effect modification based on control group supplementation or follow-up duration. CONCLUSION: There is moderate-quality evidence suggesting that prenatal vitamin D supplementation has minimal or no significant effect on reducing respiratory tract infections and allergy-related outcomes in children.