ABO haemolysis refers to haemolysis caused by incompatible ABO blood types and is seen clinically in two main situations.
The first is ABO haemolysis caused by blood group incompatibility transfusion, which has become rare with the standardisation of transfusion therapy.
The second is ABO neonatal haemolytic disease, an alloimmune haemolytic disease caused by immunisation against blood group antigens as a result of maternal-infant blood group incompatibility.
The disease almost invariably occurs in babies born to O-positive mothers with A or B blood types. When the foetus has an A or B blood type, the A or B antigen in the foetal blood enters the mother’s body for some reason and stimulates the mother to produce blood group antibodies, which then enter the foetus through the placenta and bind to the A or B antigen in the foetus, causing the foetal red blood cells to clump and then lyse, resulting in ABO haemolysis.
It also occurs rarely in babies born to A mothers with B blood type and in babies born to O mothers with AB blood type.