Gestational Diabetes (GDM). A type of diabetes that develops only during pregnancy and usually disappears upon delivery, but increases the mother's risk of developing diabetes later in life. GDM is managed with meal planning, physical activity, and, in some cases, medication.estational Diabetes (GDM). A type of diabetes that develops only during pregnancy and usually disappears upon delivery, but increases the mother's risk of developing diabetes later in life. GDM is managed with meal planning, physical activity, and, in some cases, medication.