Background: There is currently convincing clinical and experimental evidence that a hyperglycemic intrauterine environment is responsible not only for significant short-term outcomes in the fetus and newborn infant, but it is also an increased risk for long-term outcomes, such as developing diabetes mellitus and other chronic diseases in adulthood. Short-term complications can occur in utero (i. e. diabetic fetopathy, fetal macrosomia, intrauterine growth restriction, congenital malformations, intrauterine fetal death); during labor (shoulder dystocia, birth injuries, intranatal death) and during the neonatal period (respiratory distress syndrome, metabolic, electrolytic and hematological disorders, hypertrophic cardiomyopathy, neonatal mortality). The risk of adverse outcomes is greater in pre-gestational diabetes, but undiagnosed and / or poorly controlled gestational diabetes can lead to similar consequences. Although there is currently a relatively clear view on the pathogenesis of fetal and neonatal complications of maternal diabetes and their interconnections, the deep molecular mechanisms are far from being clearly understood. Furthermore, there has been an unexpected increase in the incidence of gestational diabetes worldwide during the last decades, in association with the obesity pandemic and type 2 diabetes. Conclusions: Maternal diabetes, especially pre-gestational diabetes has a significant impact on the incidence of fetal and neonatal complications with both short and long-term outcomes.