INS and gestational diabetes: Gestational diabetes mellitus (GDM) is kind of abnormal glucose tolerance during pregnancy1 and the prevalence is higher in western countries,2 but increasing year by year also in Asia,3,4 while the frequency of recurrent GDM in subsequent pregnancies is up to 50%.5 Early studies suggested that the pathogenesis of GDM is a defect of islet beta cell functions and insulin resistance.