Normal pregnancy: respiratory changes: 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: respiratory changes

Sample item

Which respiratory change is expected in a healthy woman at term?

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

The answer and the reasoning

D. Reduced functional residual capacity with increased tidal volume

Tidal volume and minute ventilation rise under progesterone drive, while the raised diaphragm reduces expiratory reserve volume, residual volume and functional residual capacity. PaCO2 falls to about 30 mm Hg with a compensated respiratory alkalosis.

Option by option

  • A. Increased residual volume

    Residual volume falls, not rises.

  • B. Compensated metabolic acidosis with a high PaCO2

    PaCO2 is low, with respiratory alkalosis compensated by renal bicarbonate loss.

  • C. Decreased minute ventilation

    Minute ventilation rises by about 30 to 50 per cent.

  • D. Reduced functional residual capacity with increased tidal volume (correct)

    Correct. Tidal volume rises and FRC falls as the diaphragm is elevated.

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 D, Reduced functional residual capacity with increased tidal volume. Tidal volume and minute ventilation rise under progesterone drive, while the raised diaphragm reduces expiratory reserve volume, residual volume and functional residual capacity.

Why is "Increased residual volume" not the answer?

Residual volume falls, not rises.

Why is "Compensated metabolic acidosis with a high PaCO2" not the answer?

PaCO2 is low, with respiratory alkalosis compensated by renal bicarbonate loss.

Why is "Decreased minute ventilation" not the answer?

Minute ventilation rises by about 30 to 50 per cent.

What concept does this question test?

It tests Normal pregnancy: respiratory changes in OBG. PaCO2 falls to about 30 mm Hg with a compensated respiratory alkalosis.

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: respiratory changes?

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.