Vitamin D and risk of preterm birth: Up‐to‐date meta‐analysis of randomized controlled trials and observational studies

Aim We performed a meta‐analysis of randomized controlled trials (RCT) and observational studies to answer the two following questions: (i) whether low maternal circulating 25 hydroxyvitamin D (25‐OHD) is associated with an increased risk of preterm birth (PTB) or spontaneous PTB (sPTB); and (ii) whether vitamin D supplementation alone during pregnancy can reduce the risk of PTB. Methods Literature search was carried out using Pubmed, Web of...