Select the INCORRECT statements with reference to Rh grouping. I. Erythroblastosis foetalis is a condition observed having foetus with Rh-ve blood and mother with Rh+ve blood. II. Rh antigen is observed on RBCs in the majority of human beings. III. Before blood transfusion, Rh group should also be matched. IV. Rh incompatibility is observed when a pregnant mother is Rh-ve and the foetus is Rh+ve. V. Erythroblastosis foetalis can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the second child. Choose the correct answer from the options given below:

Rh Incompatibility

Rh பொருந்தாமை

NCERT Class 11 · Body Fluids and Circulation · 1 NEET question

Rh incompatibility is not a random error; it is a lethal immunological mismatch. If an Rh-negative mother carries an Rh-positive fetus, her immune system treats the fetal blood as a foreign pathogen. This is a classic case of maternal-fetal alloimmunization.

The idea

Rh grouping depends on the presence of the Rh antigen on the surface of RBCs. When an Rh-negative mother is exposed to Rh-positive blood during the first delivery, she develops anti-Rh antibodies. In subsequent pregnancies, these IgG antibodies cross the placenta and destroy the fetal RBCs. This leads to severe anaemia and jaundice, a condition clinically termed erythroblastosis foetalis.

Why it matters

It is a clinical consequence of the immune system recognizing foreign Rh antigens during pregnancy, requiring medical intervention.

NEET lens

NEET focuses on the 'subsequent pregnancy' clause. Remember, the first pregnancy is usually safe because the antibody titre is low. Questions often test the specific antibody type (IgG) and the condition name. Do not confuse Rh incompatibility with ABO incompatibility; focus on the Rh antigen presence.

Clinical significance

The destruction of fetal RBCs causes haemolytic disease of the newborn. The fetus suffers from severe jaundice and anaemia, often leading to heart failure or death. Prophylactic administration of anti-Rh antibodies (RhoGAM) to the mother immediately after the first delivery prevents this immune response.

Introduction

Rh incompatibility occurs when an Rh-negative mother is sensitized to Rh-positive fetal blood, producing anti-Rh antibodies that can cross the placenta in subsequent pregnancies and destroy fetal RBCs — causing Erythroblastosis Fetalis.

Core concept

Rh factor: antigen on RBC surface. Rh+ = have antigen (85% population). Rh- = lack antigen. Unlike ABO, no pre-formed antibodies against Rh. Sensitization sequence: 1st pregnancy: Rh- mother + Rh+ fetus → at delivery, fetal RBCs enter maternal blood → mother produces anti-Rh IgG antibodies (sensitization). 2nd pregnancy: Rh+ fetus → maternal anti-Rh IgG crosses placenta (IgG can cross, IgM cannot) → destroys fetal RBCs → Erythroblastosis Fetalis. Symptoms: hemolytic anemia, jaundice, edema in fetus → can be fatal.

Go deeper

Prevention: Anti-D immunoglobulin (RhoGAM) given to Rh- mother within 72 hours of delivery (or after miscarriage, amniocentesis) → destroys fetal RBCs before mother can mount immune response → prevents sensitization → 2nd pregnancy is safe. Treatment of affected fetus: intrauterine blood transfusion (Rh- blood to fetus) or exchange transfusion after birth.

From Class 10

Another blood group system beyond ABO is the Rh system. When an Rh-negative mother carries an Rh-positive baby, serious problems can arise — this is Rh incompatibility.