ABO hemolytic disease in newborns is caused by a mismatch between the mother’s and child’s ABO blood types. It occurs mainly when the mother has O blood type and the baby has A or B blood type, the chance of occurrence is about 20%, and the chance of occurrence in a second child is about 50%. ABO hemolysis is caused by the dominant fetal red blood cell antigen inherited from the father but not from the mother, which enters the mother’s body through the placenta and stimulates the mother to produce antibodies, and when the antibodies enter the fetal blood circulation, they bind to the corresponding antigen of its red blood cells and are destroyed by the mononuclear macrophage system, causing Hemolysis.