Materials and methods: In this cross-sectional study, fasting serum levels of 25(OH)D, insulin, glucose, HOMA-IR, hs-CRP and TNF-α were measured in 45 GDM and 45 NGT women at week 20-30 gestation whom referred to Reference Medical Laboratory of Ahvaz, Iran in 1394. The gene discussed is INS; the disease is gestational diabetes.