First-trimester maternal vitamin D status and risk for gestational diabetes (GDM) a nested case-control study

Background Vitamin D deficiency may contribute to impaired glucose metabolism. There are sparse data regarding vitamin D and the development of gestational diabetes (GDM). The objective of this study was to assess if first-trimester vitamin D deficiency is more prevalent in women later diagnosed with GDM compared with women with uncomplicated pregnancies. Methods We conducted a nested case-control study of pregnant women who had previously given blood for routine genetic multiple marker screening and subsequently delivered at a tertiary hospital between November 2004 and July 2009. From an overall cohort of 4225 women, 60 cases of GDM were matched by race/ethnicity with 120 women delivering at term (>= 37 weeks) with uncomplicated pregnancies. Banked maternal serum was used to measure maternal 25-hydroxyvitamin D [25(OH)D]. Results The prevalence of first-trimester maternal vitamin D deficiency (defined as 25(OH)D < 50 nmol/L) was comparable among women with GDM compared with controls (5/60 vs 8/120, p = 0.90). The median 25(OH)D level for all subjects was 89 nmol/L (interquartile range, 73-106 nmol/L). Seventy three percent (117/160) of the cohort had 25(OH)D levels = 75 nmol/L. Conclusions In a cohort of pregnant women with mostly sufficient levels of serum 25(OH)D, vitamin D deficiency was not associated with GDM. Further studies are warranted with larger cohorts, especially in populations with lower levels of vitamin D. Copyright (C) 2011 John Wiley & Sons, Ltd.