High blood sugar in pregnant women may cause effects such as fetal gigantism, immature fetal lung development and fetal malformation. 1. Fetal macrosomia: high blood glucose in pregnant women will reach the fetus through the already formed placenta, resulting in proliferation and hypertrophy of fetal islet cells and secretion of more insulin. Under the action of hyperinsulinemia and increased blood glucose, the fetus will develop excessively, forming a baby larger than the gestational age, and presenting as a huge baby at birth. 2. Fetal lung immaturity: when hyperglycemia exists in late pregnancy, the fetus is prone to neonatal hypoglycemia and neonatal lung immaturity after birth. 3. Fetal malformations: The incidence of severe fetal malformations in pregnant women with uncontrolled pre-pregnancy diabetes is 7-10 times higher than in normal pregnancies, and is closely related to high blood glucose levels in the first few weeks after conception. Therefore, when pregnant women have high blood sugar, it is recommended that they go to the obstetrics department of a regular hospital for timely examination and standardized treatment.