In some cases, fetal red blood cells of different blood types enter the maternal circulation and stimulate the mother to produce antibodies, which can enter the fetal blood circulation through the placental villi, destroying fetal red blood cells and leading to fetal hemolysis. Clinically, the following are common: 1. ABO blood group incompatibility, which is the main cause of hemolysis in newborns. The mother is type O and the husband is type A, B or AB, which is clarified by testing the blood types of both parties; 2. Rh blood group incompatibility: the husband is RH-positive blood type and the pregnant woman is RH-negative blood type, which is clarified by testing the Rh blood type. When there is ABO blood group incompatibility or Rh blood group incompatibility, it is necessary to test the serum of pregnant women to see if there are immune antibodies and their potency; if there are immune antibodies and their potency is high, it can be diagnosed as mother-child blood group incompatibility.