Lower vitamin D levels during the second trimester are associated with developing gestational diabetes mellitus: an observational cross-sectional study

In this study, we aimed to compare serum 25(OH)D levels in women with and without gestational diabetes mellitus (GDM), and to identify the serum 25(OH)D levels associated with GDM. We recruited 40 women with GDM and 40 healthy pregnant women, aged 20–40 years and in the second trimester, at Gulhane Education and Research Hospital. We excluded women with chronic diseases, preeclampsia, pre-GDM, multiple pregnancies, and those taking medications...