Vitamin D deficiency in pregnancy and gestational diabetes mellitus

OBJECTIVE: We examined the association of second-trimester maternal plasma 25-hydroxyvitamin D (25[OH] D) during pregnancy with gestational diabetes mellitus (GDM). STUDY DESIGN: Among 1314 pregnant women who participated in Project Viva, a birth cohort study, we measured 25(OH) D levels at 26-28 weeks gestation during GDM screening using a 1-hour 50-g glucose challenge test. RESULTS: We found 25(OH) D levels of <25 nmol/L in 44 of 1087 women (4.0%) with normal glucose tolerance, 9 of 159 women (5.7%) with impaired glucose tolerance, and 9 of 68 women (13.2%) with GDM. Analyses that were adjusted for sociodemographics, season, maternal body mass index, gestational weight gain, and dietary factors suggested that women with 25(OH) D levels of <25 vs >= 25 nmol/L may have higher odds of experiencing GDM (odds ratio, 2.2; 95% confidence interval, 0.8 -5.5). Glucose levels after the glucose challenge test were associated inversely with 25(OH) D levels (P < .01). CONCLUSION: Second-trimester 25(OH) D levels were associated inversely with glucose levels after 1-hour 50-g glucose challenge test; low 25(OH) D levels may be associated with increased risk of GDM.