Diabetes is a condition in which the body can't make enough insulin, or can't use insulin normally. Insulin is a hormone. It helps sugar (glucose) in the blood get into cells of the body to be used as fuel. When glucose can’t enter the cells, it builds up in the blood. This leads to high blood sugar (hyperglycemia). High blood sugar can cause problems all over the body. It can damage blood vessels and nerves. It can harm the eyes, kidneys, and heart. In early pregnancy, high blood sugar can lead to birth defects in a growing baby. Some women have diabetes before they get pregnant. This is called pregestational diabetes. Other women may get a type of diabetes that only happens in pregnancy. This is called gestational diabetes. Pregnancy can change how a woman's body uses glucose. This can make diabetes worse, or lead to gestational diabetes.