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