Normal pregnancy: supine hypotension: 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: supine hypotension

Sample item

A 34-week primigravida becomes pale, sweaty and dizzy with a blood pressure of 80/50 mmHg when she lies flat for an ultrasound. The pressure normalises on turning her to the left. What is the mechanism?

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

The answer and the reasoning

B. Compression of the inferior vena cava by the gravid uterus reducing venous return

In the supine position the gravid uterus compresses the inferior vena cava, which reduces venous return and cardiac output and causes supine hypotensive syndrome. Turning to the left lateral position or tilting the uterus relieves the compression. The same principle applies during resuscitation and caesarean section.

Option by option

  • A. Vasovagal response to the ultrasound gel

    A vasovagal response would not be so clearly position-dependent.

  • B. Compression of the inferior vena cava by the gravid uterus reducing venous return (correct)

    Correct. IVC compression lowers preload, and left lateral position relieves it.

  • C. Compression of the abdominal aorta causing raised afterload

    Aortic compression reduces uterine perfusion but does not explain the maternal hypotension relieved by turning.

  • D. Sudden amniotic fluid embolism

    Amniotic fluid embolism does not resolve with positional change.

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, Compression of the inferior vena cava by the gravid uterus reducing venous return. In the supine position the gravid uterus compresses the inferior vena cava, which reduces venous return and cardiac output and causes supine hypotensive syndrome.

Why is "Vasovagal response to the ultrasound gel" not the answer?

A vasovagal response would not be so clearly position-dependent.

Why is "Compression of the abdominal aorta causing raised afterload" not the answer?

Aortic compression reduces uterine perfusion but does not explain the maternal hypotension relieved by turning.

Why is "Sudden amniotic fluid embolism" not the answer?

Amniotic fluid embolism does not resolve with positional change.

What concept does this question test?

It tests Normal pregnancy: supine hypotension in OBG. Turning to the left lateral position or tilting the uterus relieves the compression. The same principle applies during resuscitation and caesarean section.

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 Normal pregnancy: supine hypotension?

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.