Female blood type AB and male type O usually do not cause hemolysis.
Fetal hemolysis, commonly known as ABO hemolysis, occurs mostly when the woman is type O and the man is type B, A, or AB. There is a possibility of hemolysis when the child is type A, B or AB.
However, there is a case of RH hemolysis, which can easily occur if the mother has RH negative blood and the fetus has RH positive blood, and when the mother is pregnant with her second child, the fetus has Rh positive blood. After hemolysis occurs, anemia, jaundice, hepatosplenomegaly, and in severe cases, heart failure may occur. Immunoglobulin or albumin is needed, and blood exchange therapy may be performed.
Therefore, hemolysis does not usually occur when a woman is type ab and a man is type o.