It is well known that the mother’s blood type is many times different from the child’s blood type. Blood types are mainly classified according to the blood group antigens contained in human blood, and each person’s blood type is regularly inherited from the parents. For example, if a person has A antigen in his blood, he has A blood type; if he has B antigen, he has B blood type; if he has both A antigen and B antigen, he has AB blood type; if he has neither A antigen nor B antigen, he has O blood type. In addition to the blood group antigens mentioned above, there is also a corresponding substance in the blood – blood group antibodies; type A blood has anti-B antibodies and type B blood has anti-A antibodies. Blood group tests are routinely performed on women who have prenatal checkups, and confusion usually follows after learning their blood type, especially for a woman with blood type O who may be carrying a non-O baby if she marries a non-O man. For example, with a type O woman and a type A man, the baby may be type O or A, while with a type O woman and a type B man, the baby may be type O or B. With a type O woman and a type AB man, the baby may be type A or B. In this way, the blood types of the pregnant mother and the fetus may be different, so will hemolysis occur? The blood group antigens (e.g. A antigen and B antigen of ABO blood group) that the fetus inherits from the father may happen to be lacking in the mother. Throughout pregnancy, and especially at the time of delivery, fetal blood inevitably enters the mother’s body, and it has been found that a very small amount of fetal blood contains enough blood group antigens to cause the mother to produce the appropriate antibodies. The initial antibodies formed are of the IgM type, which are too large to pass the placental barrier and are only present in the mother’s circulation. As time passes, the antibody type changes from IgM to IgG, which is small enough to pass through the placenta and enter the fetal circulation during another pregnancy, theoretically causing intrauterine hemolysis or neonatal hemolysis. If pregnant women with O blood type are screened for hemolysis, the lab test may show that they already have anti-A or anti-B antibodies in their bodies, and antibodies can even be found in the blood of some women who have no history of childbirth. This is because in daily life, some foods, gram-negative bacteria, intestinal parasites, vaccines, etc. also have A or B blood group substances, and continuous immune stimulation can cause the body to produce IgG anti-A or anti-B antibodies. In fact, this antibody needs to reach a certain titer, currently considered to be at least 1:64 for fetal hemolysis to occur, and 1:512 for fetal hemolysis to be highly suspected. Moreover, we often find in clinical practice that the titer of the antibody on the laboratory test is not proportional to the degree of fetal hemolysis; more often than not, the antibody titer may be high, but the baby is safe. The likelihood of a lady with type O marrying a non-type O man is quite high. Before marriage, older people may seek Daisy’s approval for their children’s birth date, and it is also popular in modern times to look at their respective horoscopes, but I have never heard of checking the blood type before marriage to see if they can get married and have children. Moreover, the objective fact observed by medical research data is that the incidence of hemolytic disease due to ABO blood group incompatibility is very low, and even if there is mild hemolysis, severe fetal edema rarely occurs in utero, and after the baby is born, the jaundice is mainly mild, similar to physiological jaundice, and it is easy to help the baby pass easily through the treatment methods familiar to pediatrics, such as blue light irradiation. Therefore, if there is no history of delivering a jaundiced or edematous newborn, no history of recurrent miscarriage, premature birth, or fetal death in utero, and no women who have received blood transfusions, they can be checked for ABO blood type, but routine screening of women for anti-A or anti-B blood group antibodies is not advocated, which means that there is no need for routine ABO hemolysis testing in the general population. In addition, in our body, there is another blood group system that is very important for medical research, but not much known by the general public, that is, the Rh blood group system, which is only positive and negative, the majority of people are Rh positive, Rh negative rate varies among different people and races, about 15% of Americans, about 5% of blacks, 0.34% of Han Chinese, some ethnic minorities may be more than 5% ( Rh-negative blood types are often referred to as “panda blood” to emphasize their rarity and rarity, and serious maternal and child blood type incompatibility occurs mainly in Rh-negative mothers, and only in cases where the mother is Rh-negative and the father is Rh-positive, and the baby in the womb happens to be Rh-positive. From the perspective of eugenics, we recommend all women to be tested for Rh factor before delivery, and for Rh-negative women married to Rh-positive husbands, they need strict perinatal management, regular Coomber’s test to monitor the intrauterine condition of the fetus, and even if the first child is safe and sound, anti-D immunoglobulin injections should be given on time under the guidance of the doctor to protect the next child from The first child is safe, and the next child is protected from hemolysis by regular injections of anti-D immunoglobulin under doctor’s supervision.