Can hemolysis occur if the husband has type O blood and the wife has type AB blood?

Blood type differences between parents can potentially cause hemolytic disease of the newborn, although this situation does not necessarily occur. When the father has type O blood and the mother has type AB blood, their child may inherit either type A or type B blood, and generally, there won't be direct blood type incompatibility causing hemolysis in these cases.

Hemolytic disease of the newborn mainly occurs when a mother's blood contains antibodies against the infant's blood cells. This typically happens within the Rh blood group system. If the mother is Rh-negative and the father is Rh-positive, their first child may be Rh-positive, and the mother's body might then produce antibodies against Rh-positive blood. During a subsequent pregnancy, if the fetus is again Rh-positive, these antibodies may cross the placenta into the fetal circulation and attack the fetus's red blood cells, causing hemolysis.

However, in the ABO blood group system, humans have a natural tolerance, and antibodies against ABO blood types typically are not produced even if the mother's and child's blood types differ. Therefore, a child born to a mother with type O blood and a father with type AB blood generally will not develop hemolytic disease due to ABO blood type incompatibility.