Gynaecological endocrinology: luteal phase length: 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 · Gynaecological endocrinology: luteal phase length

Sample item

A woman has regular 35-day cycles. On approximately which day does she ovulate?

ADay 28BDay 21CDay 14DDay 35

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

The answer and the reasoning

B. Day 21

The luteal phase is relatively constant at about 14 days because it is governed by the lifespan of the corpus luteum, whereas the follicular phase varies. Ovulation therefore occurs about 14 days before the next menses, which is day 21 in a 35-day cycle. This is why day 14 is correct only for 28-day cycles.

Option by option

A. Day 28
Day 28 would leave only 7 days for the luteal phase.
B. Day 21 (correct)
Correct. 35 minus 14 gives day 21.
C. Day 14
Day 14 applies to a 28-day cycle.
D. Day 35
Day 35 is the day of the expected next period.

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 B, Day 21. The luteal phase is relatively constant at about 14 days because it is governed by the lifespan of the corpus luteum, whereas the follicular phase varies.

Why is "Day 28" not the answer?

Day 28 would leave only 7 days for the luteal phase.

Why is "Day 14" not the answer?

Day 14 applies to a 28-day cycle.

Why is "Day 35" not the answer?

Day 35 is the day of the expected next period.

What concept does this question test?

It tests Gynaecological endocrinology: luteal phase length in OBG. Ovulation therefore occurs about 14 days before the next menses, which is day 21 in a 35-day cycle. This is why day 14 is correct only for 28-day cycles.

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 Gynaecological endocrinology: luteal phase length?

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.