title: Maternal vitamin D status during pregnancy and risk of childhood asthma: A meta-analysis of prospective studies.
abstract: 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.
  
  
  
  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.
  
  
  
  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.
authors.affiliation: Department of Epidemiology, School of Public Health, Shandong University, Jinan, P.R. China.
authors.forename: Huihui
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Epidemiology, School of Public Health, Shandong University, Jinan, P.R. China.
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.affiliation: Department of Epidemiology, School of Public Health, Shandong University, Jinan, P.R. China.
authors.forename: Chongqi
authors.initials: C
authors.lastname: Jia
mesh_terms: D001249:Asthma / Q000097:blood* / Q000209:etiology; D002648:Child; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D039382:Maternal Nutritional Physiological Phenomena; D011247:Pregnancy; D012307:Risk Factors; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000150:complications
chemical_list: D014807:Vitamin D
keywords: Childhood asthma; Maternal; Meta-analysis; Vitamin D