Reproduction: luteal-placental shift: practice question

A Physiology 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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Physiology · Reproduction: luteal-placental shift

Sample item

A woman at 6 weeks of pregnancy loses the pregnancy after removal of the corpus luteum, whereas the same procedure at 11 weeks does not end pregnancy. What explains the difference?

ARising maternal LH sustains ovarian progesterone after the corpus luteum is removedBBy 8 to 10 weeks the placenta produces enough progesterone to replace the corpus luteumCBy 8 to 10 weeks the decidua stores enough progesterone for the remainder of pregnancyDBy 8 to 10 weeks the fetal adrenal produces all required progesterone

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

The answer and the reasoning

B. By 8 to 10 weeks the placenta produces enough progesterone to replace the corpus luteum

hCG from the syncytiotrophoblast rescues the corpus luteum, which makes progesterone early in pregnancy. Around 8 to 10 weeks the placenta takes over steroidogenesis (the luteal-placental shift), so luteectomy after this time is tolerated. hCG peaks at about 8 to 10 weeks and then falls.

Option by option

A. Rising maternal LH sustains ovarian progesterone after the corpus luteum is removed
LH is suppressed in pregnancy and cannot maintain ovarian progesterone.
B. By 8 to 10 weeks the placenta produces enough progesterone to replace the corpus luteum (correct)
Correct. Placental progesterone synthesis takes over from the corpus luteum.
C. By 8 to 10 weeks the decidua stores enough progesterone for the remainder of pregnancy
The decidua does not store a progesterone reserve sufficient for the pregnancy.
D. By 8 to 10 weeks the fetal adrenal produces all required progesterone
The fetal adrenal supplies precursors (DHEA-S) for oestriol, not the bulk of progesterone.

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 Physiology question

What is the answer to this Physiology question?

The best answer is B, By 8 to 10 weeks the placenta produces enough progesterone to replace the corpus luteum. hCG from the syncytiotrophoblast rescues the corpus luteum, which makes progesterone early in pregnancy.

Why is "Rising maternal LH sustains ovarian progesterone after the corpus lut…" not the answer?

LH is suppressed in pregnancy and cannot maintain ovarian progesterone.

Why is "By 8 to 10 weeks the decidua stores enough progesterone for the remai…" not the answer?

The decidua does not store a progesterone reserve sufficient for the pregnancy.

Why is "By 8 to 10 weeks the fetal adrenal produces all required progesterone" not the answer?

The fetal adrenal supplies precursors (DHEA-S) for oestriol, not the bulk of progesterone.

What concept does this question test?

It tests Reproduction: luteal-placental shift in Physiology. Around 8 to 10 weeks the placenta takes over steroidogenesis (the luteal-placental shift), so luteectomy after this time is tolerated. hCG peaks at about 8 to 10 weeks and then falls.

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 Reproduction: luteal-placental shift?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.