Individuals with Rh antigens present on RBCs are Rh positive and those without it are Rh negative. If Rh −ve mother bears an Rh +ve child during first pregnancy when mother’s blood is exposed to Rh +ve antigens, then anti − Rh antibodies are produced in her blood. During subsequent pregnancies, these antibodies may destroy RBCs of the foetus. This results in severe anaemia and jaundice to new born. This condition is called erythroblastosis foetalis. During Rh incompatibility, the first child is safe or may have anaemia. However, this condition can be avoided for subsequent pregnancies by administering anti-Rh antibodies of mother immediately after delivery of first child. Thus to prevent the death of foetus, it is necessary to check the mothers blood for the presence of Rh antibodies.
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