The effects of diabetes mellitus on the fetus are as follows: First, giant fetuses. The incidence of giant fetus is as high as 25%-42%. It is mainly because of the high blood glucose of pregnant women, the fetus is in the environment of hyperinsulinemia due to maternal hyperglycemia for a long period of time, and the effect of protein, fat synthesis and inhibition of lipid lowering leads to excessive development of the carcass. Second, fetal growth restriction. The incidence is about 21%. Hyperglycemia in early pregnancy has an inhibitory effect on embryonic development, leading to backward embryonic development in early pregnancy and affecting the fetus. Third, miscarriage and preterm labor. High blood sugar in early pregnancy can make the embryo develop abnormally, leading to embryonic death and miscarriage. If combined with excessive amniotic fluid, hypertensive disorders of pregnancy, fetal distress complications, it is necessary to terminate the pregnancy early, resulting in preterm labor, the incidence of which is about 10-25%. Fourth, fetal malformation. The incidence is much higher than that of non-diabetic pregnant women, and the incidence of severe malformations is about 7-10 times that of a normal pregnancy.