Question

In which one of the following cases, will an anti-Rh antibody treatment prevent erythroblastosis foetalis?

• A. Anti-Rh antibody to the Rh-negative mother after delivery of the first Rh-positive child
• B. Anti-Rh antibody to the Rh-positive mother after delivery of the first Rh-negative child
• C. Anti-Rh antibody to the Rh-negative mother after delivery of the first Rh-negative child
• D. Anti-Rh antibody to the Rh-positive mother after delivery of the first Rh-positive child

Hint:

Erythroblastosis foetalis only happens when Mother is Rh-negative and Baby is Rh-positive.
The mother is the one who needs protection from becoming sensitized, so the treatment (anti-Rh antibodies) is always given to the Rh-negative mother after she delivers an Rh-positive baby.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks about the clinical management and prevention of erythroblastosis foetalis (hemolytic disease of the newborn) using passive immunization with anti-Rh antibodies.

Step 2: Key Formula or Approach:
Understand the immunological basis of Rh incompatibility:
1. The disease occurs only when an Rh-negative mother carries an Rh-positive fetus.
2. Sensitization of the mother's immune system typically occurs during the delivery of the first Rh-positive baby, when fetal blood cells enter the maternal circulation.

Step 3: Detailed Explanation:
Let's explore the pathophysiology and preventive treatment:

• Pathology:
- An Rh-negative mother does not naturally have the Rh antigen on her red blood cells.
- If she carries an Rh-positive fetus, maternal and fetal blood are separated by the placenta during gestation.
- However, during parturition (delivery), there is a high likelihood of fetal red blood cells crossing into the maternal bloodstream.
- The mother's immune system recognizes these Rh-positive cells as foreign and produces memory B-cells and active anti-Rh antibodies (IgG class).
- During subsequent pregnancies with another Rh-positive fetus, these maternal IgG antibodies cross the placenta and destroy the fetal red blood cells, causing severe anemia, jaundice, or death (erythroblastosis foetalis).

• Prevention using Anti-Rh antibodies (RhoGAM):
- To prevent maternal sensitization, exogenous anti-Rh antibodies are administered to the Rh-negative mother immediately (usually within 72 hours) after the delivery of the first Rh-positive child.
- These passively administered antibodies bind to and clear any fetal Rh-positive red blood cells present in the mother's circulation before her own immune system can recognize them and initiate an immune response.

Step 4: Final Answer:
The treatment must be given to an Rh-negative mother after delivering an Rh-positive child, corresponding to option (A).