When women with type 1 or type 2 diabetes become pregnant, the primary concern is that the extra sugar in the mother's blood will be delivered to the baby during the first six weeks of pregnancy, increasing the risk of heart and neural tube defects. (Birth defects are not a concern with gestational diabetes because it occurs later in pregnancy, usually between 24 and 28 weeks, after major organs have formed.)
Beyond birth defects, other risks to the baby are the same for type 1, type 2, or gestational diabetes. If the mother's blood sugar levels are high, the baby is "fed" excess sugar and grows too large, and a large baby can result in premature birth, birth trauma, or cesarean delivery. Additionally, when the baby gets excess sugar, his pancreas produces extra insulin, which may continue after birth and result in dips in the newborn's blood sugar levels.