First-Trimester Circulating 25-Hydroxy Vitamin D Levels and Development of

OBJECTIVE—To investigate the association between first-trimester maternal serum levels of 25-hydroxy vitamin D (25-OH-D) as measured by liquid chromatography-tandem mass spec-trometry and development of gestational diabetes mellitus (GDM). RESEARCH DESIGN ANDMETHODS—We conducted a case-control study involving 248 women in the first-trimester of pregnancy, 90 of whom developed GDM and 158 remained normoglycemic. RESULTS—Although 25-OH-D levels correlated negatively with 2-h glucose post-oral glucose tolerance test and positively with HDL cholesterol, as well as with ethnicity, obesity, and smoking (all P, 0.05), there were no statistically significant differences in baseline maternal mean 25-OH-D levels between those who subsequently developedGDM18.9 ng/mL (10.7) and thosewho remained normoglycemic 19.0 ng/mL/L (10.7) (P = 0.874), even after adjustment for possible confounders including sampling month (P = 0.784). CONCLUSIONS—Our large andwell-phenotyped prospective study did not find evidence of an association between first-trimester maternal levels of 25-OH-D and subsequent development of GDM