Erythroblastosis foetalis : Maternal-foetal Rh incompatibility Maternal-foetal
incompatibility results when an Rh- woman, married to an Rh+ man conceives a child
who is Rh+. If the man’s genotype is DD, all of their offspring (Dd) will be Rh+. If the
man’s genotype is Dd, half of their offspring with Dd genotype will be Rh+. If RBC of
Rh+ foetus cross the placental barrier and enter into Rh- mother’s blood stream, the
mother’s immune system reacts to the foetal Rh antigen stimulus by producing a large
number of anti - Rh antibodies. When mother’s anti - Rh antibodies seep through
placenta into blood circulation of foetus, they start hemolysis (break down / bursting)
of RBC of foetus. As this destruction continues, the foetus becomes anaemic. The
anaemic foetus starts to release many -immature erythroblasts into his blood stream.
That is why this hemolytic disease of the new bom is called erythroblastosis foetalis.
This anaemia may lead to .abortion or still birth. Even if the pregnancy continues,
the liver and spleen of the foetus swell as they rapidly produce RBC. The breakdown
product of RBC called bilirubin also accumulates in the foetus. Bilirubin damages his
brain cells and turns his skin and whites of the eye yellow. This condition is jaundice.
So the baby if born alive, suffer from severe hemolytic anaemia and jaundice. Such
baby’s blood should be immediately replaced by Rh” blood free of anti - Rh antibodies.
The first Rh incompatible pregnancy may not face much problems if very few of foetal
antigens cross placenta into maternal circulation and the amount of maternal antibody
production is not very high. But when placenta detaches at birth, a large number of
foetal cells enter mother’s blood stream and stimulate production of large amount of
anti - Rh antibodies by the mother. These anti - Rh antibodies persist in mother’s blood
for a long time and are persistent risk for the next Rh+ foetus. Rh sensitization of Rh’
mother is avoided by a simple therapy. She is given an injection of Rh antiserum during
early pregnancy and immediately after birth. The Rh - antibodies in the Rh antiserum
will destroy Rh+ RBC of the foetus before they stimulate production of maternal anti -
Rh antibodies. The injected antiserum disappears before the next pregnancy
Sometimes a mild ABO incompatibility protects the baby against a more severe Rh
incompatibility. If O’ mother conceives A+ or B+ baby, any^ foetal A or B type RBC
entering the mother’s blood are quickly destroyed by her anti - A or anti - B antibodies,
before she can form anti - Rh antibodies.
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