Vitamin D Status in Pregnant Women in Southern China and Risk of Preterm Birth: A Large-Scale Retrospective Cohort Study

Background The influence of maternal vitamin D on pregnancy outcomes, including preterm birth (PTB), is unclear due to different experimental designs and study populations (patient race and sample size) of previous studies. We aimed to investigate the relationship between 25-hydroxyvitamin D (25[OH] D) levels and PTB among pregnant women in southern China.