Vitamin D may play a bigger role in pregnancy than simply supporting bone health.A new study suggests that optimizing vitamin D levels before and during pregnancy may improve outcomes for both mother and baby.An analysis of more than 15,000 pregnancies found that women with the lowest vitamin D levels had the highest risk of preterm birth—defined as delivery before 37 weeks.The link was especially pronounced in very preterm births—those occurring before 32 weeks.Researchers say randomized clinical trials are needed to determine whether optimizing vitamin D during pregnancy can reduce the risk of this complication.In the meantime, the authors say women with limited sun exposure may want to talk to their health care provider about their vitamin D levels and potential supplementation.Prior research by members of the same team suggests vitamin D may also help with development of the placenta and reduce the risk of other serious pregnancy complications such as preeclampsia and gestational diabetes.Source: Journal of Perinatology Author Affiliations: Medical University of South Carolina .Sign up for our weekly HealthDay newsletter