Gestational diabetes is a temporary form of insulin resistance that usually occurs halfway through a pregnancy as a result of excessive hormone production in the body, or the pancreas' inability to make the additional insulin that is needed during some pregnancies in women without a previous history of Type 1 or Type 2 diabetes. Gestational diabetes usually goes away after pregnancy, but women who have had gestational diabetes are at an increased risk for later developing Type 2 diabetes. Researchers have identified a small percentage of diabetes cases that result from specific genetic syndromes, surgery, chemicals, drugs, malnutrition, infections, viruses and other illnesses. Excess blood sugar levels can also be harmful for the growing fetus.