Recently, there is a new saying: before getting married, you should not only investigate the other party’s looks, occupation and family background, but also pay attention to the blood type of the target, in case you are not careful and the parents’ blood type does not match and causes hemolytic reactions in the newborn, that would be bad. As a hematologist, I am often asked by patients who are in a hurry to have a baby: “Dr. Liu, can you please help us to see if our blood types are compatible? Will the child be hemolyzed after the birth? ……”, as if I were a fortune teller. In my years of practice, I have occasionally seen a few cases of hemolysis in newborns due to blood type incompatibility with the mother. It is like falling from heaven to hell, and before you can taste the joy of the child’s arrival, you are caught in the anxiety of running for medical attention. In recent years, with the improvement of the quality of life and the promotion of eugenics, more and more couples have started to pay attention to the various dangerous situations that may occur during pregnancy, and this has led me to pay more attention to this issue. The origin of blood type Blood type, to put it mildly, represents different characteristics of people, such as A blood type is aggressive, B blood type is agile, O blood type is stubborn, AB blood type is cautious, and this is used to deduce the character and fortune of people with different blood types. From the medical point of view, blood type usually refers to the type of specific antigen on the red blood cell membrane. Since the first human blood group system, the ABO blood group system, was discovered in 1901, 25 different red blood cell blood group systems have been discovered to date. The more important blood group systems in medicine are ABO, Rh, MNSs, Kell, Duff, etc. Among them, the most clinically relevant are the RH blood group system and the most well-known ABO blood group system. The ABO blood group system is based on the presence or absence of A and B antigens on the red blood cell membrane, and blood is classified into four types: A type if the red blood cell membrane contains only A antigens; B type if it contains only B antigens; AB type if it contains both A and B antigens; and O type if it has neither A nor B antigens. The distribution of blood group antigens in the population varies depending on the region and ethnicity. The sera of people with different blood types contain different antibodies, but they do not contain antibodies corresponding to their own red blood cell antigens. If the blood of two people with incompatible blood types is mixed, the red blood cells can agglomerate into clusters, which is medically called “red blood cell agglutination”, and under the action of complement, the agglutinated red blood cells can be caused to rupture, resulting in hemolysis. The mechanism of hemolysis in newborns The occurrence of hemolysis is essentially the result of a synergistic effect of antigen-antibody reaction and complement. Antibodies are immunoglobulins that are produced by the body’s immune system for defense after exposure to exogenous antigenic stimuli and bind specifically to the antigen. There are two types of ABO blood group antibodies: natural antibodies and immune antibodies. Natural antibodies generally cannot reach the fetus through the placenta and do not cause coagulation and destruction of the fetal red blood cells, which explains why they do not cause fetal hemolysis despite the inconsistent blood type of the mother and fetus. However, immune antibodies can enter the fetus through the placenta, leading to the destruction of fetal red blood cells and the occurrence of neonatal hemolysis. Such antibodies are produced by the mother due to the entry of exogenous A or B antigens into the body in the past. This can be seen in cases where the A or B blood group antigen inherited from the father enters the mother’s O blood group through the placenta (at the time of delivery), stimulating the mother to produce the corresponding immune antibodies, and when another pregnancy occurs (where the fetus has the same ABO blood group as the previous one), the immune antibodies will enter the fetus’ blood through the placenta, leading to neonatal hemolysis. In addition, due to the existence of natural A and B blood group substances in nature, such as certain parasites and bacterial toxins, O mothers have received stimulation from A or B blood group substances before their first pregnancy, and the immune antibodies in the blood can enter the fetal blood circulation and cause hemolysis. The Rh blood group system is different from the ABO blood group system, which is divided into RH-positive and RH-negative. 99% of the Han Chinese and most other ethnic groups are Rh-positive and do not contain Rh antibodies in their bodies. When an Rh-negative pregnant woman carries an Rh-positive fetus, the fetal antigens can enter the mother’s body, causing the mother to produce immune antibodies, and when she carries an Rh-positive fetus for the second time, these antibodies can enter the fetal blood through the placenta, causing hemolytic anemia in the newborn and seriously endangering the life of the affected child. ABO hemolytic disease theoretically does not occur in the mother’s AB type or the baby’s O type, but mainly occurs in the mother’s O type and the fetus’ A, B or AB blood type, which can develop in the first child with mild clinical manifestations, while Rh hemolytic disease usually occurs in the second child with severe clinical manifestations. Presentation and prevention of hemolysis in newborns ABO hemolysis mainly causes jaundice, while Rh hemolysis causes severe anemia and even heart failure in fetuses. It has been reported that ABO hemolysis accounts for more than 85% of neonatal hemolysis, while the more dangerous Rh hemolysis accounts for only about 10% due to the rare antigenic type. Although maternal and infant ABO blood group incompatibility is relatively common, but not all O blood type women married with A or B or AB blood type male child will occur neonatal hemolytic disease. According to the information reported, the statistical ABO blood type incompatibility pregnancy in China accounts for 26.2% of the total number of births, and only 5% or less of those with symptoms, which is like a small probability event as it is often said in statistics. Therefore women who are already pregnant or planning to get pregnant generally do not have to worry about their babies suffering from ABO hemolysis. Although excessive worry is unnecessary, it is worth mentioning that pregnant women and their husbands who have had newborns with severe jaundice and anemia or who have a history of stillbirth should undergo ABO and Rh blood tests as well as related antibody tests and bilirubin concentration tests in amniotic fluid, etc. For Rh blood group incompatibility, pregnant women should have their blood tested for Rh blood group antibodies at 16 weeks of gestation and every 2-4 weeks thereafter, and if the antibody potency If the potency of the antibodies gradually increases, it indicates the possibility of Rh hemolytic disease. Lastly, I would like to say that it is not terrible if the blood types of couples do not merge. As long as pre-conception screening and mid-pregnancy testing are done well, and if problems are detected, timely consultation with a specialist and effective treatment can be provided, the chance of newborn hemolysis caused by blood group incompatibility can be greatly reduced. We wish every couple can have a healthy and lovely baby and share the joy of family.