Normal pregnancy and antenatal care: blood pressure in pregnancy: 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: blood pressure in pregnancy

Sample item

A healthy normotensive woman has blood pressure readings of 100/60 mmHg at 20 weeks, lower than her pre-pregnancy values, although cardiac output has risen. What mainly explains this?

AA fall in systemic vascular resistance due to vasodilatationBCompression of the inferior vena cava by the uterusCA reduction in blood volumeDA fall in cardiac output

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

The answer and the reasoning

A. A fall in systemic vascular resistance due to vasodilatation

Cardiac output rises by 30 to 50 percent in pregnancy, but progesterone, nitric oxide and the low-resistance placental bed lower vascular resistance, so pressure dips and is lowest in mid-pregnancy. It returns towards the pre-pregnancy level by term. A failure of this fall is an early sign of hypertensive disease.

Option by option

A. A fall in systemic vascular resistance due to vasodilatation (correct)
Correct. Vasodilatation lowers resistance more than the output rises.
B. Compression of the inferior vena cava by the uterus
Vena caval compression causes supine hypotension late in pregnancy and only when lying flat.
C. A reduction in blood volume
Blood volume actually increases by 40 to 50 percent.
D. A fall in cardiac output
Cardiac output is increased, not reduced.

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 OBG question

What is the answer to this OBG question?

The best answer is A, A fall in systemic vascular resistance due to vasodilatation. Cardiac output rises by 30 to 50 percent in pregnancy, but progesterone, nitric oxide and the low-resistance placental bed lower vascular resistance, so pressure dips and is lowest in mid-pregnancy.

Why is "Compression of the inferior vena cava by the uterus" not the answer?

Vena caval compression causes supine hypotension late in pregnancy and only when lying flat.

Why is "A reduction in blood volume" not the answer?

Blood volume actually increases by 40 to 50 percent.

Why is "A fall in cardiac output" not the answer?

Cardiac output is increased, not reduced.

What concept does this question test?

It tests Normal pregnancy and antenatal care: blood pressure in pregnancy in OBG. It returns towards the pre-pregnancy level by term. A failure of this fall is an early sign of hypertensive 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 Normal pregnancy and antenatal care: blood pressure in pregnancy?

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.