When the mother’s blood type is O and the husband’s blood type is something other than O, such as A, B, or AB, and the fetus is conceived with blood type A or B, we call it ABO blood group incompatibility, and in this case, neonatal hemolysis is likely to occur. Why does ABO hemolysis occur? There are four types of human ABO blood groups: A, B, O and AB; those with A antigen on their red blood cells are A, those with B antigen on their red blood cells are B, those with both A and B antigen on their red blood cells are AB, and those without A and B antigen on their red blood cells are O. A mother with O blood does not have A and B antigen on her red blood cells; when she is pregnant with a fetus with A or B blood type, the mother will be affected by the blood type of the fetus. This antibody can enter the fetus through the placental barrier and bind specifically to the A or B antigen on the fetal red blood cells, resulting in the destruction of the fetal red blood cells (i.e. hemolysis). Therefore, when the mother’s blood type is O and the husband is not O, the fetus should be checked for blood type immediately after birth. Not every child will develop the disease, and if the child’s blood type is O, the possibility of occurrence is minimal. If the child does have ABO hemolysis, prompt treatment is required. In addition, it is recommended that pregnant women have their blood tested for antibody titers by 20 weeks of pregnancy. The potency of the antibodies can be used as a reference indicator for the development of hemolysis in the newborn, but it is not necessarily a parallel relationship. Treatment is usually not required during pregnancy. However, the potency of antibodies during pregnancy is high enough to take Chinese (herbal) medicine, and some pregnant women have the need to take it until delivery, even for the baby. Pay attention to the jaundice of the newborn within the first 24 hours after delivery. Even if jaundice occurs, mostly mild or moderate jaundice, individual severe neonatal hemolysis, the first time after delivery to the baby blood exchange, the success rate is higher. Blood exchange, of course, is decided and prepared before you give birth (especially if hemolytic death occurs in the first child).