Hemolysis may occur when the blood groups of the fetus and the mother do not match. When the fetus is growing and developing in the uterus, because of the incompatibility between the fetus’s blood group and the mother’s blood group (including Rh and ABO), some of the fetus’s red blood cells may enter the mother’s body and stimulate the production of antibodies in the mother’s blood system. The production of antibodies in the mother’s body will result in a hemolytic reaction. When fetal hemolysis occurs most of the time, it will lead to fetal anemia, and may also cause fetal jaundice, liver and spleen enlargement, and in severe cases, may even cause fetal death in the womb. Fetal hemolysis occurs mostly in the mother’s blood type Rh-negative blood or in the mother’s type O and the fetus type A or B. Rh hemolytic disease does not usually occur in the first trimester . Therefore, it is important to have regular checkups during pregnancy to detect the blood type of the pregnant woman, consult a doctor in time if there is any discomfort, and pay attention to the fetal movement, and under the guidance of a professional doctor, so as to avoid delaying the condition.