Type of diabetes mellitus which is unmasked or discovered during pregnancy and usually goes away after the baby is born.During pregnancy the concentration of the harmones ( progeterone,oestrogen cortisol and human placental lactogen etc.) in the blood is increased.These harmones have strong anti-insulinic effect ,as these harmones compete with insulin for receptors on the cells.Secondly the meternal insulin is degraded by placental insulinases(ant-insulinic enzymes).All these factors contribute to the increased insulin resistance during pregnancy.Risk factors for development of gestational diabetes (GDM) are as follows:- a. History of diabetes in previous pregnancies. b. Positive family history of diabetes(siblings and parents). c. History of delivery of a large baby(>4kgs.) d. Age (>30 years) e.Obesity(weight gain>15% of non pregnant ideal weight) f. History of still birth or unexplained misscarriages. g. Others. Gestational diabetes is usually mild and initially well managed by diet and exercise,but some may require insulin.Anti-diabetic medication like Sulphonylureas are not recommended during pregnancy and this is due to the fact that these drugs cross placental barrier and may cause hypoglycemia in baby,therefore insulin is the drug of choice for diabetes during pregnancy if not controlled by diet and exercise. For the diagnosis of gestational diabetes read :- HOW IS DIABETES MELLITUS DIAGNOSED The ideal time to perform screening test for gestational diabetes is between 24th-28th week.For high risk women the test should be repeated at 32th week.Women who have past history of gestational diabetes need screening at 18th-22th weeks. About 40-50% of women with gestational diabetes develop diabetes in future and their offsprings have more chances of getting diabetes.Uncontrolled gestational diabetes may lead to increased incidence of macrosomia(big baby).These babies are prone to birth trauma due to excessive fat accumulation on shoulders and trunk.Except brain all other organs may be affected by macrosomia.It should be noted that fetal congenital anomalies are not increased due to gestational diabetes because there is no metabolic disturbance at the time of organogenesis(when the organs of the baby are formed).