Gestational diabetes mellitus (GDM) is one of the most common complications in pregnancy. It affects 3-15% of women, depending on the background diabetes risk of the population and applied diagnostic criteria. GDM is associated with neonatal problems such as macrosomia and neonatal hypoglycemia as well as a long term increased risk of diabetes and obesity of offspring. Current therapy of GDM focuses on tightly controlling maternal glucose levels, resulting in insulin therapy in up to 50% of women to reach the fasting glucose target of < 90 mg/dl and 2h-postprandial glucose < 120 mg/dl. However, the rate of macrosomia and C-sections remains increased in pregnancy with GDM despite therapy. This review introduces the diagnosis and implications of GDM and then examines two strands of research aimed at improving current therapy: first, research into predictive markers of GDM pregnancies requiring intensified insulin therapy, and second, research into hypoglycaemic agents for therapy or even prevention of GDM in high risk women such as women with polycystic ovarian syndrome. Predictive markers include amniotic fluid insulin, which requires an invasive amniocentesis procedure, and measures of fetal abdominal circumference early in the third trimester, which have successfully been used to reduce rates of macrosomia. Potential hypoglycemic agents include glyburides and metformin, which have been shown not to have adverse outcomes on neonates, although oral agents are generally contra-indicated because of possible teratogenic and toxic effects observed in animal studies and missing long term outcome data.