ABO hemolysis refers to homozygous immune hemolysis caused by the incompatibility of mother and baby’s blood type. 99% of the time, it occurs in pregnant women with blood type O, and it is easy to occur when the husband’s blood type is A, B, or AB, and the fetus’s blood type is A, B. The fetus may have anemia, heart enlargement, liver and spleen enlargement, and edema of the fetus and placenta. Hemolysis can cause fetal anemia, heart enlargement, hepatosplenomegaly, edema of the fetus and placenta, increased red blood cells in the blood, severe fetal hypoxia caused by fetal death in the womb, the newborn will also appear jaundice, indirect bilirubin can pass the blood-brain barrier to make the brain nerve nuclei yellow, affecting the intellectual development and neurological function. the normal range of ABO hemolysis is less than 1:128, in the ABO system, because the O-type people have anti-A or anti-BigG, more than the A type people with anti-A or anti-BigG. In the ABO system, because the number of O-type people with anti-A or anti-BigG is more than the number of A-type and B-type people, and the antigenicity of A antigen is stronger than that of B antigen, therefore, the mother is O-type and the fetus is A-type people have more chances to get the disease, and when the antibody is more than 1:128, we should be alert to the possibility of hemolysis.