Diabetes mellitus (DM) is a chronic disease that needs medical support and continuing patient education to avoid acute complications and decrease the long-term complications. The prevalence of diabetes is high in many areas, especially Asian. There are many risk factors for developing gestational diabetes, such as advanced gestational age, obesity, family history of DM, and previous delivery of large weight baby. There is higher perinatal morbidity and mortality in untreated cases, but this can be reduced with proper antepartum surveillance and adequate insulin treatment. This article consisted of an acceptable definition, pathogenesis, screening, risk factors, management of diabetes during pregnancy, maternal and fetal complication, and prevention.