This study aimed to evaluate the association between TCF7L2 and GDM in a Chinese Han population, especially because there had some unique characteristics in Chinese Han diabetic population15: Rapid growth of incidence of diabetes mellitus, more higher in post plasma glucose compared to increased fast plasma glucose, rapidly progressive failure of pancreatic islet beta cell in Han population compared to Western populations, growing number of elderly pregnant women, lower body mass index with mild insulin resistance. The gene discussed is TCF7L2; the disease is Insulin resistance.