Mounting evidence suggests that maternal vitamin D status during pregnancy may be associated with development of childhood asthma, but the results are still inconsistent. A dose–response meta-analysis was performed to quantitatively summarize evidence on the association of maternal vitamin D status during pregnancy with the risk of childhood asthma.Methods and results:
A systematic search was conducted to identify all studies assessing the association of maternal 25-hydroxyvitamin D (25(OH)D) during pregnancy with risk of childhood asthma. The fixed or random-effect model was selected based on the heterogeneity test among studies. Nonlinear dose–response relationship was assessed by restricted cubic spline model. Fifteen prospective studies with 12 758 participants and 1795 cases were included in the meta-analysis. The pooled relative risk of childhood asthma comparing the highest versus lowest category of maternal 25(OH)D levels was 0.87 (95% confidence interval, CI, 0.75–1.02). For dose–response analysis, evidence of a U-shaped relationship was found between maternal 25(OH)D levels and risk of childhood asthma (Pnonlinearity = 0.02), with the lowest risk at approximately 70 nmol/L of 25(OH)D.Conclusion:
This dose–response meta-analysis suggested a U-shaped relationship between maternal blood 25(OH)D levels and risk of childhood asthma. Further studies are needed to confirm the association.