Diabetes that develops during pregnancy is known as gestational diabetes. It occurs because your body cannot produce enough insulin (a hormone important in controlling blood glucose) to meet its extra needs in pregnancy. This results in high blood glucose levels. Gestational diabetes usually starts in the middle or towards the end of pregnancy.
Weight along with well-regulated blood sugar, your weight and weight gain during pregnancy have a big influence on the weight your fetus gains. The higher your BMI is and the more weight you gain during pregnancy, the more your fetus will gain also. Therefore, there is a risk that the fetus will be overweight even before birth. It is a good idea to aim for a small weight gain in the first half of the pregnancy, so there is room for a greater weight gain in the second half of pregnancy.