Early Pregnancy Maternal Vitamin D Concentrations and Risk of Gestational Diabetes Mellitus

Background While associations of vitamin D deficiency with type 2 diabetes have been well demonstrated, investigations of vitamin D and risk of gestational diabetes mellitus (GDM) reported inconsistent findings. We examined associations of vitamin D status with GDM. Methods In a nested case‐cohort study (135 GDM cases and 517 non‐GDM controls), we measured maternal serum vitamin D status (total 25[OH]D and 25[OH]D3) in early pregnancy (16 weeks on average) using liquid chromatography‐tandem mass spectroscopy. GDM was diagnosed according to the American Diabetes Association guidelines. We calculated adjusted odds ratios and 95% confidence intervals (CIs) using logistic regression models. Results GDM cases had lower mean total 25[OH]D (27.3 vs. 29.3 ng/mL) and 25[OH]D3 (23.9 vs. 26.7 ng/mL) concentrations compared with women who did not develop GDM (both P‐values