Radiation safety and radiobiology: sensitivity of the fetus at 8 to 15 weeks: practice question

A Radiology 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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Radiology · Radiation safety and radiobiology: sensitivity of the fetus at 8 to 15 weeks

Sample item

A pregnant woman's fetus is exposed to a very high radiation dose 10 weeks after conception. Which long-term outcome is characteristic of exposure at this stage?

ASevere intellectual disability and microcephalyBSpontaneous loss of the pregnancy within daysCMajor limb malformationsDNo effects whatever the dose

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

The answer and the reasoning

A. Severe intellectual disability and microcephaly

Between about 8 and 15 weeks the developing cortex is most sensitive, and high doses cause intellectual disability and microcephaly. Pre-implantation exposure produces an all-or-none effect, and organogenesis carries a risk of malformation.

Option by option

A. Severe intellectual disability and microcephaly (correct)
Correct. Neuronal migration in the 8 to 15 week window is highly sensitive to radiation.
B. Spontaneous loss of the pregnancy within days
Loss of the conceptus is the typical outcome of exposure in the first two weeks, before implantation.
C. Major limb malformations
Limb malformations are characteristic of exposure during early organogenesis, not at 10 weeks.
D. No effects whatever the dose
Very high doses above the threshold do cause effects, and this stage is a sensitive one.

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 Radiology question

What is the answer to this Radiology question?

The best answer is A, Severe intellectual disability and microcephaly. Between about 8 and 15 weeks the developing cortex is most sensitive, and high doses cause intellectual disability and microcephaly.

Why is "Spontaneous loss of the pregnancy within days" not the answer?

Loss of the conceptus is the typical outcome of exposure in the first two weeks, before implantation.

Why is "Major limb malformations" not the answer?

Limb malformations are characteristic of exposure during early organogenesis, not at 10 weeks.

Why is "No effects whatever the dose" not the answer?

Very high doses above the threshold do cause effects, and this stage is a sensitive one.

What concept does this question test?

It tests Radiation safety and radiobiology: sensitivity of the fetus at 8 to 15 weeks in Radiology. Pre-implantation exposure produces an all-or-none effect, and organogenesis carries a risk of malformation.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Radiation safety and radiobiology: sensitivity of the fetus at 8 to 15 weeks?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.