Normal pregnancy and antenatal care: anti-D after sensitisation: practice question

A OBG 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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OBG · Normal pregnancy and antenatal care: anti-D after sensitisation

Sample item

A Rh-negative primigravida at 20 weeks has a positive indirect Coombs test with anti-D antibodies at a titre of 1:64. She asks if anti-D immunoglobulin will protect the fetus. What is the correct answer?

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

The answer and the reasoning

B. No, because she is already sensitised; the fetus needs surveillance with Doppler

Anti-D immunoglobulin prevents sensitisation but cannot reverse it once antibodies have formed. A sensitised woman is managed by titres and serial middle cerebral artery Doppler to detect fetal anaemia, with intrauterine transfusion if needed. The father being Rh-negative would mean the baby is Rh-negative, but that does not apply to explaining her antibodies.

Option by option

  • A. Yes, but only if given within 72 hours of delivery

    The 72-hour postnatal window applies to prophylaxis in unsensitised women and does not help in sensitisation.

  • B. No, because she is already sensitised; the fetus needs surveillance with Doppler (correct)

    Correct. Prophylaxis is useless after antibodies exist, so the fetus is monitored for anaemia.

  • C. Yes, a dose now will lower the titre and protect the fetus

    Anti-D immunoglobulin does not reduce an established antibody titre.

  • D. No, because anti-D is needed only if the husband is Rh-negative

    This is backwards: prophylaxis matters when the fetus may be Rh-positive, and it is of no use once antibodies exist.

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.

More OBG questions

Questions about this OBG question

What is the answer to this OBG question?

The best answer is B, No, because she is already sensitised; the fetus needs surveillance with Doppler. Anti-D immunoglobulin prevents sensitisation but cannot reverse it once antibodies have formed.

Why is "Yes, but only if given within 72 hours of delivery" not the answer?

The 72-hour postnatal window applies to prophylaxis in unsensitised women and does not help in sensitisation.

Why is "Yes, a dose now will lower the titre and protect the fetus" not the answer?

Anti-D immunoglobulin does not reduce an established antibody titre.

Why is "No, because anti-D is needed only if the husband is Rh-negative" not the answer?

This is backwards: prophylaxis matters when the fetus may be Rh-positive, and it is of no use once antibodies exist.

What concept does this question test?

It tests Normal pregnancy and antenatal care: anti-D after sensitisation in OBG. A sensitised woman is managed by titres and serial middle cerebral artery Doppler to detect fetal anaemia, with intrauterine transfusion if needed. The father being Rh-negative would mean the baby is Rh-negative, but that does not apply to explaining her antibodies.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Normal pregnancy and antenatal care: anti-D after sensitisation?

Learn management algorithms as steps: PPH, eclampsia, ectopic pregnancy. Then use the flashcards and the other OBG 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.