Gestational diabetes mellitus (GDM) is defined as glucose intolerance that is first detected during pregnancy. It is typically mild and asymptomatic, but it can lead to perinatal complications and long-term health issues in both the mother and the child. GDM is detected through screening for clinical risk factors and, if necessary, by testing for abnormal glucose tolerance. The condition is associated with a broad spectrum of physiological and genetic abnormalities similar to those seen in non-pregnant diabetes. Women with GDM are at high risk for developing diabetes later in life, making GDM a valuable opportunity to study early diabetes pathogenesis and develop preventive interventions. Historically, GDM was recognized as a transient condition affecting fetal outcomes, but it is now understood to be a form of hyperglycemia resulting from inadequate insulin supply to meet tissue demands. The condition is linked to chronic insulin resistance, which is common during pregnancy, and β-cell dysfunction. GDM can be categorized into three subtypes: autoimmune, monogenic, and those occurring on a background of insulin resistance. Most women with GDM have chronic insulin resistance, which may be influenced by obesity and other factors. The clinical management of GDM focuses on standard antidiabetic treatments to normalize maternal glucose levels and minimize fetal overnutrition. Postpartum care aims to reduce the risk of diabetes and detect and treat any that develops. Classification of patients into subtypes can aid in clinical management, and genetic testing for specific mutations is being developed for monogenic forms of GDM. Future research should focus on understanding the mechanisms underlying GDM and its progression to diabetes, including the role of genetic and environmental factors. Studies on gene-environment interactions and insulin action in muscle and fat may provide insights into the causes of insulin resistance and lead to more effective prevention and treatment strategies.Gestational diabetes mellitus (GDM) is defined as glucose intolerance that is first detected during pregnancy. It is typically mild and asymptomatic, but it can lead to perinatal complications and long-term health issues in both the mother and the child. GDM is detected through screening for clinical risk factors and, if necessary, by testing for abnormal glucose tolerance. The condition is associated with a broad spectrum of physiological and genetic abnormalities similar to those seen in non-pregnant diabetes. Women with GDM are at high risk for developing diabetes later in life, making GDM a valuable opportunity to study early diabetes pathogenesis and develop preventive interventions. Historically, GDM was recognized as a transient condition affecting fetal outcomes, but it is now understood to be a form of hyperglycemia resulting from inadequate insulin supply to meet tissue demands. The condition is linked to chronic insulin resistance, which is common during pregnancy, and β-cell dysfunction. GDM can be categorized into three subtypes: autoimmune, monogenic, and those occurring on a background of insulin resistance. Most women with GDM have chronic insulin resistance, which may be influenced by obesity and other factors. The clinical management of GDM focuses on standard antidiabetic treatments to normalize maternal glucose levels and minimize fetal overnutrition. Postpartum care aims to reduce the risk of diabetes and detect and treat any that develops. Classification of patients into subtypes can aid in clinical management, and genetic testing for specific mutations is being developed for monogenic forms of GDM. Future research should focus on understanding the mechanisms underlying GDM and its progression to diabetes, including the role of genetic and environmental factors. Studies on gene-environment interactions and insulin action in muscle and fat may provide insights into the causes of insulin resistance and lead to more effective prevention and treatment strategies.