Biology · Body Fluids and Circulation · NEET
The MOTHER is Rh-NEGATIVE and the FOETUS is Rh-POSITIVE. This is the single most tested point. NCERT states the incompatibility is between the 'Rh-ve blood of a pregnant mother with Rh+ve blood of the foetus'. If you reverse these two (mother +ve, baby -ve), the statement is WRONG. NTA loves to flip this. The Rh+ve foetus gets the Rh antigen from an Rh+ve father.
During the first pregnancy the mother's Rh-ve blood and the foetus's Rh+ve blood are kept separate by the placenta, so the mother is not exposed to the Rh antigen. During the DELIVERY of the first child, small amounts of Rh+ve foetal blood leak into the mother. She then starts making anti-Rh antibodies. In her NEXT pregnancy these antibodies leak into the Rh+ve foetus and destroy its RBCs. So it is the second (and later) Rh+ve child that is harmed, not the first.
The placenta separates the bloods only well enough to prevent large-scale mixing. The problem is the antibodies the mother has ALREADY made after the first delivery. Anti-Rh antibodies are small enough to cross the placenta from mother to foetus. So it is not foetal blood entering the mother this time; it is the mother's ready-made anti-Rh antibodies leaking INTO the Rh+ve foetus and destroying its RBCs.
They are given immediately AFTER the delivery of the FIRST child, not the second. This is another common NTA flip. The injected anti-Rh antibodies destroy any Rh+ve foetal cells that entered the mother during that first delivery before her own immune system can react and make memory antibodies. If you wait until the second child, the mother has already been sensitised and the damage is done.
ABO grouping uses A and B antigens with NATURAL antibodies (anti-A, anti-B) present from birth. Rh incompatibility uses the Rh (D) antigen, and Rh-ve people have NO natural anti-Rh antibodies; they only make them AFTER exposure to Rh+ve blood. That delay is exactly why the first Rh+ve baby escapes and the second is at risk. Erythroblastosis foetalis is an Rh problem, not an ABO problem.
Select the incorrect statement with reference to Rh grouping. A. Erythroblastosis foetalis is a condition observed having foetus with Rh-ve blood and mother with Rh+ve blood. B. Rh antigen is observed on RBCs in the majority of human beings. C. Before blood transfusion, Rh group should also be matched. D. Rh incompatibility is observed when a pregnant mother is Rh-ve and the foetus is Rh+ve. E. Erythroblastosis foetalis can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the second child.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is destruction of an Rh-positive foetus's RBCs by the anti-Rh antibodies of its Rh-negative mother, causing anaemia and jaundice in the baby.
Nearly 80 per cent of humans carry the Rh antigen on their RBCs and are Rh-positive; the remaining roughly 20 per cent are Rh-negative (NCERT).
The Rh antigen was first found similar to one present in Rhesus monkeys, so it is named after 'Rh'esus.
Yes. Giving anti-Rh antibodies to the Rh-ve mother immediately after the delivery of her first child destroys leaked Rh+ve foetal cells before she becomes sensitised, protecting later pregnancies.
The mother's anti-Rh antibodies destroy the foetal RBCs. This can be fatal to the foetus or cause severe anaemia and jaundice in the newborn.
