The probability of hemolysis between a mother with O blood type and a father with B blood type is 50%. The probability of hemolysis needs to be determined by the blood type of the child. If the child is blood type O, there is no possibility of hemolysis, if the child is blood type B, there may be hemolysis, so the chance of occurrence is 50%. Neonatal hemolysis is caused by mother and infant blood type incompatibility, blood antibodies in mother’s blood enter the fetal circulation through the placenta, causing homozygous immune hemolysis. The categories of neonatal hemolysis are ABO blood type hemolysis and Rh blood type hemolysis, with clinical manifestations such as jaundice and anemia. I. Categories: 1. ABO hemolysis: ABO hemolysis is a common hemolytic disorder in which the blood type of the newborn does not match that of the mother, accounting for about 85% of neonatal hemolytic disease, the first child has more incidence, the more deliveries the higher the incidence, and more serious than once. Most of them occur in the mother’s O type and the fetus’s B or A type, because A and B blood group substances are more widely existed in nature, so O blood group mothers may have been exposed to A and B substance stimulation before pregnancy, and the corresponding antibodies are produced in the serum, and this antibody enters the fetus again through the placenta and combines with the A or B antigen in the fetus, thus causing fetal red blood cell agglutination and subsequent dissolution and hemolysis; 2. hemolysis: Rh hemolysis is less common, accounting for about 15% of neonatal hemolysis. Generally Rh hemolysis is more serious than ABO hemolysis, and the incidence is relatively low. The mother’s blood type must be Rh-negative and the fetus’ blood type is Rh-positive. The red blood cells of the Rh-positive fetus enter the Rh-negative mother and can stimulate the mother to produce antibodies, but because the antibodies are produced slowly, the first child is generally unaffected and the second child is prone to hemolysis. However, if an Rh-negative mother has received a transfusion of Rh-positive blood type during the birth of the first child, hemolysis may also occur in the first child. Clinical manifestations: 1. jaundice: neonatal hemolysis is mainly due to the incompatibility of the blood type of the child and the mother, so that the fetus is born with a large number of red blood cell destruction, red blood cell destruction will have a large amount of bilirubin released into the blood, there will be obvious jaundice performance, jaundice appears earlier, lasts longer, the degree is heavier; 2. anemia: because the child’s body is a large number of red blood cells are destruction, causing the body anemia, the degree varies. If the child has severe anemia, it will be accompanied by pale skin, edema and prone to heart failure; 3. Other: fetuses with Rh hemolysis usually have different degrees of hepatosplenomegaly. Meanwhile, newborns with severe hemolysis can cause pathological damage to brain tissue through the blood-brain barrier due to high bilirubin in the blood, with neurological symptoms such as drowsiness and decreased muscle tone, which may cause death if not treated in time.