Objective: To estimate the associations between maternal vitamin D status and adverse pregnancy outcomes.

Study design: We searched electronic databases of the human literature in PubMed, EMBASE and the Cochrane Library up to October, 2012 using the following keywords: “vitamin D” and “status” or “deficiency” or “insufficiency” and “pregnancy”. A systematic review and meta-analysis were conducted on observational studies that reported the association between maternal blood vitamin D levels and adverse pregnancy outcomes including preeclampsia, gestational diabetes mellitus (GDM), preterm birth or small-for-gestational age (SGA).

Results: Twenty-four studies met the inclusion criteria. Women with circulating 25-hydroxyvitamin D [25(OH)D] level less than 50 nmol/l in pregnancy experienced an increased risk of preeclampsia [odds ratio (OR) 2.09 (95% confidence intervals 1.50–2.90)], GDM [OR 1.38 (1.12–1.70)], preterm birth [OR 1.58 (1.08–2.31)] and SGA [OR 1.52 (1.08–2.15)].

Conclusion: Low maternal vitamin D levels in pregnancy may be associated with an increased risk of preeclampsia, GDM, preterm birth and SGA.