Mothers with gestational diabetes mellitus (GDM) are at high lifetime risk of developing type 2 diabetes mellitus. The magnitude of risk for cardiovascular disease after GDM is less well established. Recently, intervention trials using lifestyle modification or medications used to treat type 2 DM have successfully prevented/delayed development of DM in women after GDM. Offspring of mothers with GDM are at risk for development of obesity and abnormal glucose metabolism during childhood, adolescence, and adulthood. Factors responsible for these risks are not fully understood. Having fetal hyperinsulinism is a risk factor for development of both obesity and abnormal glucose metabolism, and might be implicated in pathophysiology. It remains to be established whether the long-term effects of exposure to diabetes mellitus during intrauterine development can be prevented.