The prevalence of diabetes and impaired glucose tolerance in women of childbearing age is increasing worldwide, particularly among minority youth. As a consequence, in many parts of the world the number of pregnancies complicated by Type 2 diabetes is actually exceeding those complicated by Type 1 diabetes. Moreover, also the prevalence and incidence of gestational diabetes mellitus have been rising over recent years. Although diabetes complicating pregnancy is a cause of maternal and foetal complications, its exact prevalence in pregnancy is yet not well defined and large population studies are still lacking. This article reviews the existing epidemiologic studies on diabetes in pregnancy performed in Italy.