ABO hemolysis is not likely to occur when both parents have type O blood, but Rh hemolysis may occur. ABO hemolysis mainly occurs when the mother has type O blood and the fetus is type A or B. According to the law of genetics, both parents have type O blood, and the fetus also has type O blood, so there is no blood group incompatibility resulting in ABO hemolysis. However, hemolysis may occur due to Rh blood group incompatibility. There are six antigens in the Rh blood group system: D, E, C, c, d, and e. Rh hemolytic disease may occur if the mother has the D antigen but lacks the other antigens in the Rh system, and the fetus has these antigens. Therefore, both parents are O-type blood, generally do not occur ABO hemolysis, there is the possibility of Rh hemolysis, the specific situation is recommended to go to the hospital to consult the doctor in detail.