ABO Hemolytic Disease: It occurs when the mother’s blood type is O and the father’s blood type is A, B, or AB. The blood type of the fetus is determined by a combination of genes passed from each parent, so the fetus may have a different blood type than the mother. For example, if a mother with blood type O carries a fetus with blood type A inherited from the father, due to the absence of A antigen in the mother’s body with blood type O, when the red blood cells of the fetus with blood type A enter into the mother’s body, the mother’s body will produce anti-A antibody, and the anti-A antibody enters into the baby’s body and causes the destruction of the baby’s red blood cells and hemolysis. However, not all babies born to mothers with blood type O will develop hemolytic disease, but some babies will develop the disease and some babies will not develop the disease, some have mild symptoms and some have severe symptoms. This is related to the amount of maternal antibodies, the degree of binding of antibodies to fetal red blood cells, the strength of the A(B) antigen and the fetal compensatory hematopoietic capacity. Since there are substances similar to A(B) antigens in nature, mothers with type O blood are often exposed to them before pregnancy, and these similar blood group antigenic substances can then stimulate mothers with type O blood to produce A(B) antibodies, which can pass through the placenta into the fetus and cause hemolysis when the mother is pregnant. Clinical manifestations of hemolytic disease in newborns: Jaundice: bilirubin decomposed by the destruction of red blood cells is yellow, which can be distributed throughout the body, so that the color of the body’s tissues become yellow, due to the skin and the sclera (commonly known as the white eyeballs) is located on the surface of the body, the yellowing of the most obvious, which is also known as jaundice. Most newborns will have jaundice after birth, but when jaundice appears too early, develops too quickly, or the blood bilirubin level is too high, we should pay attention to the possibility of hemolytic disease. Jaundice in infants with hemolytic disease often appears within 24 hours of birth or on day 2. Bilirubin encephalopathy: High blood levels of bilirubin can damage brain cells and cause bilirubin encephalopathy, the most serious complication of hemolytic disease. It usually occurs 2 to 7 days after delivery and is characterized by worsening jaundice and neurological symptoms such as lethargy, feeding difficulties, double gaze and convulsions. If left untreated, it can lead to death or have sequelae such as motor dysfunction and intellectual backwardness. Anemia: Due to the destruction of red blood cells, babies with hemolysis have varying degrees of anemia. Hepatosplenomegaly: In severe hemolysis, fetal edema and marked enlargement of the liver and spleen may occur, a symptom most commonly seen in Rh hemolytic disease. Fever: Fever may be a response of the body to pediatric hemolysis or in more severe bilirubin encephalopathy. The fever may not always be high, but if it occurs as a result of the latter, it indicates that the condition has become more severe. Generally the symptoms of ABO blood group hemolysis are very mild, most of the children do not need special treatment after birth, as long as timely blue light irradiation and medication, the child’s condition can be relieved, even if it is a serious Rh hemolytic disease, if timely blood exchange, the vast majority of babies can also be turned around.