Theoretically should occur more frequently since ~1 in 4/5 babies and mothers are ABO incompatible. Usually occurs in group O mothers who may have high titres of naturally occurring IgG anti-A or B, and with a boost to this during pregnancy haemolysis can occur.

Clinical features

First pregnancies are not exempt, but condition is usually mild. Presentation is later than with Rh HDN (2-4d, but may be weeks after birth).


May be difficult—DAT commonly and puzzlingly -ve, but offending antibody can be eluted from infant RBC.

Antibody studies

Maternal high titre anti-A/B almost always in a group O mother cord-blood/infant's serum-an inappropriate antibody (e.g. anti-A in a group A baby).

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