Abstract: Risk factors of gestational diabetes mellitus（GDM）include age，obesity，ethnicity，adverse obstetrical and neonatal outcomes，and family history of diabetes. Insulin resistance plays a main role in GDM. Impact of GDM on mothers and fetals is intimately related to levels of glycaemic control. Women with GDM are increased risk of pre-eclampsia，polyhydramnios，shoulder dystocia or cephalopelvic disproportion，injury of birth canal， caesarean delivery and diabetes after years，while their infants tend to experience higher rates of macrosomia， preterm birth，morbidity and mortality. The offspring of these women are also at increased risk of obesity and metabolism syndrome in childhood.

Key words: Pregnancy, Fetus, Diabetes mellitus, Diabetes, gestational, Pregnancy complications