Infertility: basal body temperature: 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 · Infertility: basal body temperature

Sample item

A woman records her basal body temperature daily on waking. What pattern indicates that ovulation has occurred?

AA sustained rise of about 0.3 to 0.5 degrees C in the second half of the cycleBA spike on the day of menses onlyCA fall of 0.5 degrees C in the second halfDA flat chart throughout

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

The answer and the reasoning

A. A sustained rise of about 0.3 to 0.5 degrees C in the second half of the cycle

Progesterone secreted by the corpus luteum acts on the hypothalamic thermoregulatory centre and raises the basal body temperature by about 0.3 to 0.5 degrees C, producing a biphasic chart. The temperature rises after ovulation, so it identifies ovulation retrospectively and is not suitable for timing intercourse in advance. Illness and disturbed sleep can distort the readings.

Option by option

A. A sustained rise of about 0.3 to 0.5 degrees C in the second half of the cycle (correct)
Correct. A biphasic chart with a luteal rise indicates ovulation.
B. A spike on the day of menses only
A temperature spike on menses has no ovulatory meaning.
C. A fall of 0.5 degrees C in the second half
A fall in the luteal phase would suggest anovulation or low progesterone.
D. A flat chart throughout
A flat chart suggests an anovulatory cycle.

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 sustained rise of about 0.3 to 0.5 degrees C in the second half of the cycle. Progesterone secreted by the corpus luteum acts on the hypothalamic thermoregulatory centre and raises the basal body temperature by about 0.

Why is "A spike on the day of menses only" not the answer?

A temperature spike on menses has no ovulatory meaning.

Why is "A fall of 0.5 degrees C in the second half" not the answer?

A fall in the luteal phase would suggest anovulation or low progesterone.

Why is "A flat chart throughout" not the answer?

A flat chart suggests an anovulatory cycle.

What concept does this question test?

It tests Infertility: basal body temperature in OBG. 3 to 0.5 degrees C, producing a biphasic chart. The temperature rises after ovulation, so it identifies ovulation retrospectively and is not suitable for timing intercourse in advance. Illness and disturbed sleep can distort the readings.

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 Infertility: basal body temperature?

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.