Gestational diabetes happens only during pregnancy. This is because, during pregnancy, the placenta makes hormones which can lead to high sugar levels in the blood. Generally, to normalize the high blood sugar levels, the pancreas produces enough insulin. But, if the insulin production is deficient or improper, then it could lead to high sugar levels in the blood of a pregnant, thereby leading to gestational diabetes. Risk factors include family history of having diabetes, overweight before getting pregnant, PCOS, case history of gestational diabetes etc. It can be treated with a low carb diet, physical fitness and insulin injections.