Gestational diabetes mellitus (GDM) is a topic of major interest, as it affects up to 16% of pregnant women and may lead to adverse pregnancy outcomes, which, however, are preventable by appropriate treatment. The aim of the present study was to discuss basic concepts and to critically appraise recent updates on practical issues in the field of GDM. GDM pathophysiology, long-term complications including "fetal programming" and GDM diagnosis are discussed, while clinical practice guidelines on follow-up, medical nutrition therapy, oral hypoglycemic agents and insulin treatment are also reviewed. GDM comprises a serious yet preventable public health problem and prevention by lifestyle changes, early detection and adequate treatment can lead to better health outcomes for both mothers with GDM and their offspring.