Date: March 2004
Why is it, that Rh imcompatibility with mother and child
can result in erythroblastosis fetalis, but an incompatibility with blood
groups does not have the same result?
There actually CAN be incompatibilities between mother and child with different blood groups.
They aren't as severe as Rh incompatibilities, but can cause enough hemolysis of baby's blood
cells to cause jaundice. This is called ABO Hemolytic Disease of the Newborn. In Rh
incompatibility, sensitization occurs only after the second pregancy. In ABO incompatibility,
it occurs frequently with the first pregnancy. The mother is invariably type O and therefore
has both anti A and anti B. So if the fetus is Type A, the mother's anti A can cross the
placenta and attack the baby's cells. This is rarely serious and may just involve a few hours
under the bili lights, but in severe cases transfusion has been necessary.
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Update: June 2012