Rh Incompatibility and Erythroblastosis — NEET Biology
✅ Asked in NEET 2026Another antigen, the Rh antigen similar to one present in Rhesus monkeys (hence Rh), is also observed on the surface of RBCs of majority (nearly 80 per cent) of humans. Such individuals are called Rh positive (Rh+ve) and those in whom this antigen is absent are called Rh negative (Rh-ve). An Rh-ve person, if exposed to Rh+ve blood, will form specific antibodies called anti-Rh antibodies in his/her blood. Therefore, Rh grouping should be done before transfusions. A special case of Rh incompatibility (mismatching) has been observed between the Rh-ve blood of a pregnant mother with Rh+ve blood of the foetus. Rh antigens of the foetus do not get exposed to the Rh-ve blood of the mother in the first pregnancy as the two bloods are well separated by the placenta. However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of the Rh+ve blood from the foetus. This initiates the formation of anti-Rh antibodies in the blood of the mother. In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh-ve) can leak into the blood of the foetus (Rh+ve) and destroy the foetal RBCs. This could be fatal to the foetus or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis. This can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.
NTA tests your understanding of Rh incompatibility during pregnancy, specifically erythroblastosis foetalis (hemolytic disease of newborn). The key concept: an Rh-negative mother carrying an Rh-positive fetus faces danger only from the SECOND pregnancy onward, not the first. Students often mistake this and think the first baby is at risk. The trap: forgetting that placental separation protects the first fetus, but delivery allows fetal blood to mix with maternal blood, triggering antibody formation. Remember: first pregnancy = antibody formation begins; subsequent pregnancies = anti-Rh antibodies cross placenta and attack fetal RBCs. Prevention: administer anti-Rh antibodies (RhoGAM) immediately after first delivery to prevent sensitization.
Select the incorrect statement(s) about Rh grouping: A. Erythroblastosis foetalis is foetus Rh-ve, mother Rh+ve. B. Rh antigen is on RBCs of most humans. C. Rh group should be matched before transfusion. D. Rh incompatibility when mother Rh-ve and foetus Rh+ve. E. Erythroblastosis foetalis avoided by anti-Rh antibodies after delivery of second child.
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