Blood and immunity: Rh isoimmunisation: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Blood and immunity: Rh isoimmunisation

Sample item

An Rh-negative primigravida delivers an Rh-positive baby. Why is anti-D immunoglobulin given to her within 72 hours?

ATo raise the mother's IgM titreBTo block placental transfer of maternal IgGCTo suppress fetal erythropoiesisDTo destroy fetal Rh-positive cells before the mother mounts a primary immune response

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. To destroy fetal Rh-positive cells before the mother mounts a primary immune response

Fetal red cells enter the maternal circulation at delivery. Anti-D clears them before maternal B cells sensitise, preventing anti-D IgG that would cross the placenta in a later Rh-positive pregnancy and cause haemolytic disease.

Option by option

A. To raise the mother's IgM titre
The aim is to prevent a maternal antibody response, not to raise titres.
B. To block placental transfer of maternal IgG
Anti-D does not block placental transport of IgG.
C. To suppress fetal erythropoiesis
Anti-D acts on the mother's immune response, not on fetal marrow.
D. To destroy fetal Rh-positive cells before the mother mounts a primary immune response (correct)
Correct. Passive anti-D removes fetal cells and prevents active sensitisation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, To destroy fetal Rh-positive cells before the mother mounts a primary immune response. Fetal red cells enter the maternal circulation at delivery.

Why is "To raise the mother's IgM titre" not the answer?

The aim is to prevent a maternal antibody response, not to raise titres.

Why is "To block placental transfer of maternal IgG" not the answer?

Anti-D does not block placental transport of IgG.

Why is "To suppress fetal erythropoiesis" not the answer?

Anti-D acts on the mother's immune response, not on fetal marrow.

What concept does this question test?

It tests Blood and immunity: Rh isoimmunisation in Physiology. Anti-D clears them before maternal B cells sensitise, preventing anti-D IgG that would cross the placenta in a later Rh-positive pregnancy and cause haemolytic disease.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Blood and immunity: Rh isoimmunisation?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.