The blood group system can be divided into two categories, ABO blood group system and Rh blood group system. ABO blood group system classifies human blood types into four types, A, B, AB and O. And O blood type is one of them, which is called universal output blood type because it does not contain the lectin of A and B blood types but has the lectin of both. And O blood type is one of them, known as the universal output blood type because it does not contain the agglutinogen of A and B blood types, but has the agglutinin of both. The specific benefits and disadvantages are as follows: 1. Benefits: Because the red blood cells of type O blood are not agglutinated by the serum of the other three blood types, no hemolytic reaction will occur, so type O blood is called the universal blood type, and in an emergency, a small amount can be considered for other blood types, but not too much; 2. Disadvantages: Other blood types cannot give blood to type O blood, and type O blood can only receive type O blood; at the same time, if the mother is type O blood, and The baby’s blood type is A or B, which may lead to the occurrence of neonatal hemolysis, 40%-50% of which occurs in the first child. Since the mother has received external antibodies before pregnancy, but they do not exist in the fetus, hemolysis is prone to occur at birth. In addition, one’s own blood type is a congenital determinant that cannot be changed later in life. There is no need to worry about the occurrence of hemolytic reactions in blood transfusion patients, because detailed laboratory tests are performed before transfusion in each patient. And women of childbearing age with O blood type do not have to worry too much whether their future babies will suffer from hemolysis. With the development of medical technology, regular maternity checkups and hemolysis tests on time can help to exclude most congenital diseases or intervene early in neonatal hemolysis, so that the incidence of hemolysis can be gradually reduced.