High blood sugar in pregnant women may cause harm to pregnant women, fetus and newborns, including abnormal embryonic development, excessive amniotic fluid, huge fetus, hypoglycemia and other harms. 1. Harm to pregnant women: pregnant women with high blood glucose have a higher chance of abnormal embryonic development or even death, miscarriage, high risk of gestational diabetes, high blood glucose will also make pregnant women susceptible to infections, and infections may induce ketoacidosis and other acute complications. Pregnant women with high blood sugar are prone to excessive amniotic fluid in the second trimester. 2. Hazards to the fetus: High blood sugar can lead to an increase in the incidence of macrosomia, fetal growth restriction, intrauterine distress, intrauterine fetal death, and fetal malformations. 3. Harm to newborns: babies born to pregnant women with high blood sugar are prone to neonatal respiratory distress syndrome and neonatal hypoglycemia. Pregnant women with high blood sugar should go to the hospital in time, under the guidance of the doctor for dietary adjustments and medication, try to avoid the harm caused by elevated blood sugar.