A Meta-Analysis of Mean Vitamin D Concentration among Pregnant Women and Newborns in Iran

Introduction: Pregnant women and newborns are at risk of vitamin D deficiency (VDD). VDD during pregnancy can lead to several maternal and fetal complications. This study was performed with aim to determine the mean concentration of 25-hydroxyvitamin D [25(OH)D] in pregnant women and newborns in Iran. Methods: This meta-analysis study was performed without time limitation up to August 2016 based on the protocol of systematic review and meta-analysis studies (PRISMA). To access relevant studies, databases of Magiran, Iranmedex, SID, Medlib, IranDoc, Scopus, PubMed, Science Direct, Cochrane, Web of Science, CINAHL and Google Scholar were independently searched by two researchers. Search was performed using MeSH keywords. Pooled estimator was calculated according to significant I2 index based on the random effects model. Data were analyzed using Review Manager software version 5.3.5. Results: Among 19 studies, 4,829 pregnant women and 1,195 newborns were enrolled. The mean age of pregnant women was 27.01±0.31 years. Mean concentration of vitamin D in pregnant women was 15.02 ng/ml (95% CI: 13.68-16.35). This rate in newborns of 6 studies was calculated 14.59 ng/ml (95% CI: 9.94-19.23). The standardized mean difference (SMD) of 25(OH)D concentration was significant in pregnant women at third-trimester and their newborns (P=0.001). Conclusion: Mean concentration of vitamin D in pregnant women and newborns in Iran is very low and there is a direct relationship between maternal concentrations of vitamin D at third-trimester and newborn. Therefore, addressing VDD in Iranian pregnant women and newborns should be considered as a health priority.