Maternal Vitamin D Levels During Pregnancy and Their Effects on Maternal-Fetal Outcomes: A Systematic Review.

To synthesize and critically review the current evidence available on maternal vitamin D deficiency and its effects on maternal-fetal outcomes, this study reviewed the maternal-fetal outcomes, including prolonged labour or cesarean delivery, preeclampsia, gestational diabetes, low birth weight and small for gestational age, and preterm birth. An extensive systematic searched was performed in Medline and EMBASE, where a medical subject heading (MeSH) was used with terms "Vitamin D/25(OH)D" and "pregnancy/fetal outcomes"; these terms were combined with "and." In Web of Science and Google Scholar, a key word search was used. Nineteen articles were included for full review. This review found that the current state of the evidence is equivocal for maternal-fetal outcomes such as the risk of prolonged labour and cesarean delivery, gestational diabetes, low birth weight and small for gestational age, and preterm birth. Although some previous studies have found improvement in pregnancy outcomes with sufficient vitamin D levels, others have not shown any association with the aforementioned outcomes. This systematic review also highlights an association between the risk of preeclampsia and maternal vitamin D levels that is found to be consistent among studies.