Antepartum haemorrhage: vasa praevia: 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 · Antepartum haemorrhage: vasa praevia

Sample item

Painless vaginal bleeding occurs immediately after rupture of membranes with fetal bradycardia. Which test on the blood can confirm that it is fetal in origin?

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

The answer and the reasoning

B. Apt test

Vasa praevia is rupture of fetal vessels running in the membranes over the cervix. The Apt-Downey test distinguishes fetal from adult haemoglobin because fetal haemoglobin resists alkali denaturation. Immediate caesarean section is required because fetal exsanguination is rapid.

Option by option

  • A. Kleihauer-Betke test of the mother's blood

    The Kleihauer-Betke test detects fetal cells in maternal blood after fetomaternal haemorrhage.

  • B. Apt test (correct)

    Correct. The Apt test shows that the blood is fetal.

  • C. Coombs test

    The Coombs test detects antibodies.

  • D. Peripheral smear for schistocytes

    A smear does not identify the source of blood.

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.

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Questions about this OBG question

What is the answer to this OBG question?

The best answer is B, Apt test. Vasa praevia is rupture of fetal vessels running in the membranes over the cervix.

Why is "Kleihauer-Betke test of the mother's blood" not the answer?

The Kleihauer-Betke test detects fetal cells in maternal blood after fetomaternal haemorrhage.

Why is "Coombs test" not the answer?

The Coombs test detects antibodies.

Why is "Peripheral smear for schistocytes" not the answer?

A smear does not identify the source of blood.

What concept does this question test?

It tests Antepartum haemorrhage: vasa praevia in OBG. The Apt-Downey test distinguishes fetal from adult haemoglobin because fetal haemoglobin resists alkali denaturation. Immediate caesarean section is required because fetal exsanguination is rapid.

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 Antepartum haemorrhage: vasa praevia?

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.