ABO hemolysis mainly occurs when the mother is type O and the fetus is type A, B or AB, but ABO hemolysis does not occur if the mother is type AB or the baby is type “O”. The cause of ABO hemolysis is that the mother has type O blood and contains antibodies to type A and B blood. When the fetus has type A, B or AB blood, the antibodies to anti-A and anti-B in the mother’s body enter the fetus through the placenta and combine with the fetal red blood cells, causing hemolysis. Manifestations of ABO hemolysis: (1) ABO blood group discordance: It usually does not cause severe intrauterine hemolysis in the fetus due to suppressive immunity in the womb. (2) Jaundice: Jaundice is the main manifestation of ABO hemolysis, manifested by early appearance of jaundice, faster rise in indicators, and increased destruction of red blood cells. Most of them appear in the first 2 to 3 days after birth. Jaundice appears within the first day after birth in about 1/4 of cases, and similarly, severe jaundice in about 1/4 of cases. 4 to 5 days jaundice reaches its peak and is mainly moderate, with a few being severe. (3) Anemia: Patients with ABO hemolytic disease have varying degrees of anemia, but generally to a lesser degree, with severe anemia (meaning hemoglobin below 100 g/L) accounting for only about 5%. (4) Severe hemolysis can also lead to hepatosplenomegaly and fetal edema, and even nuclear jaundice. The main treatment methods: (1) blue light irradiation for jaundice; (2) intravenous infusion of propyleneglobulin neutralizing antibody; (3) blood exchange for replacement of antibody to reduce bilirubin. Characteristics of ABO hemolysis: (1) ABO hemolysis occurs in only 1/5 of newborns with maternal-child ABO blood group incompatibility. (2) ABO hemolytic disease can occur in the first trimester.