Question

RajeevCBSEX" style="float: left; margin-right: 15.640625px;"

If RH positive second faetus grows inside the uterus of RH negative mother then the child generally dies due to Erythroblastosis foetalis, but the same does not happen if mother is having blood group A and a faetus is growing inside having blood group B. Why ?

Answer 1

When the mother and the foetus have different blood groups, it can lead to erythroblastosis foetalis mainly when foetus is Rh positive and mother is Rh negative.
In Rh compatibility, mostly IgG type antibody is produced that is small and can cross the placenta easily resulting in ​erythroblastosis foetalis.

It may also occurs with other blood groups say when mother is having blood group A and foetus blood group B. But in these cases, it is rare due to the reason that the antibodies produced in the mother's body are of large size (like IgM type) which cannot cross the placenta. Thus, cannot enter into the body of feotus.

IgG may also be produced but in less quantity, so it may cross the blood and results in severe anemia or jaundice in feotus. But this can be cured with various blood transfusions.