There is a risk of hemolysis in pregnancies where the father has blood type b and the mother has blood type o. When the father has blood type b and mother has blood type o, the blood type of the fetus may be type o or type b. When the blood type of the fetus is type b, the red blood cells of the fetus can enter the mother’s body through the placenta, and the mother will produce the corresponding antibodies, which can be circulated back to the fetus through the placenta and combine with the antigens of the red blood cells of the fetus to lead to hemolysis, therefore, the father’s blood type b and the mother’s blood type o pregnancy has a risk of hemolysis. If the blood type of the fetus is o blood type, the fetus and the mother’s blood type is the same, will not occur ABO blood type hemolysis, can further improve the mother and child Rh blood type, such as Rh blood type is the same, the fetus will not occur the risk of hemolysis. If the maternity test suggests that there is a risk of hemolysis, the pregnant woman should undergo standardized treatment under the guidance of a professional physician in a timely manner, so as not to delay the condition and lead to adverse consequences.