Abstract: Objective： This study investigated the relationship between 25-hydroxyvitamin D3 concentrations and gestational diabetes mellitus at 13-16 gestational weeks. Methods： A nested case-control study of 132 cases was conducted in September 2011 at Shanghai First Maternity and Infant Hospital， Tongji University School of Medicine. Among them， 44 GDM cases were ascertained and 88 women who were not diagnosed with GDM， preeclampsia， multiple pregnancy， multiparas were selected as the control group. The concentration of serum 25-hydroxyvitamin D3 was measured at 13-16 gestational weeks. Percentiles of 25-hydroxyvitamin D3 was calculated. The corresponding mobidity of GDM was determined for each percentile cut-off point. The sensitivity， specificity， Youden index， positive predictive value， and negative predictive value were also estimated. Results：①Maternal serum 25-hydroxyvitamin D3 concentrations in GDM were significantly lower than that in the control gruop[（49.8±22.0） nmol/L vs. （63.1±22.4） nmol/L， P＜0.01].② The Youden index was the highest（22.73） when the concentrations of 25-hydroxyvitamin D3 was 45.201 0 nmol/L（P35）， OR=0.375（95% CI： 0.176-0.797）. ③ Among GDM cases， 25-hydroxyvitamin D3 difficiency were significantly correlated with hyperglycemia at 1-hour OGTT [（42.56±17.04） nmol/L vs. （55.32±23.93） nmol/L， P＜0.05]. Conclusions： The study suggest that maternal 25-hydroxyvitamin D3 deficiency at 13-16 gestational weeks is significantly associated with an elevated risk for GDM. 25-hydroxyvitamin D3 difficiency is obviously correlated with hyperglycemia at 1-hour OGTT.

Key words: Cholecalciferol, Diabetes, gestational, Glucose tolerance test