Medical genetics: prenatal diagnosis: practice question

A Anatomy 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.

Try it

Anatomy · Medical genetics: prenatal diagnosis

Sample item

A 38-year-old woman at 11 weeks of gestation has a nuchal translucency of 4 mm and wishes the earliest diagnostic karyotype. Which procedure is most appropriate?

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

The answer and the reasoning

B. Chorionic villus sampling

Chorionic villus sampling is carried out at 10 to 13 weeks and samples trophoblast, giving an early karyotype. Amniocentesis is normally performed from 15 to 18 weeks, and earlier sampling carries higher loss and talipes risk. Cell-free DNA is a screening test needing diagnostic confirmation, and cordocentesis is done later.

Option by option

  • A. Cell-free DNA screening as the diagnostic test

    Cell-free DNA analysis is a screening test and a positive result needs invasive confirmation.

  • B. Chorionic villus sampling (correct)

    Correct. It can be done at 11 weeks and yields a diagnostic result.

  • C. Fetal blood sampling from the umbilical cord

    Cordocentesis is done after about 18 weeks and carries greater risk.

  • D. Amniocentesis now

    Amniocentesis at this gestation is too early and has higher risks, and is normally done from 15 weeks.

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.

More Anatomy questions

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Chorionic villus sampling. Chorionic villus sampling is carried out at 10 to 13 weeks and samples trophoblast, giving an early karyotype.

Why is "Cell-free DNA screening as the diagnostic test" not the answer?

Cell-free DNA analysis is a screening test and a positive result needs invasive confirmation.

Why is "Fetal blood sampling from the umbilical cord" not the answer?

Cordocentesis is done after about 18 weeks and carries greater risk.

Why is "Amniocentesis now" not the answer?

Amniocentesis at this gestation is too early and has higher risks, and is normally done from 15 weeks.

What concept does this question test?

It tests Medical genetics: prenatal diagnosis in Anatomy. Amniocentesis is normally performed from 15 to 18 weeks, and earlier sampling carries higher loss and talipes risk. Cell-free DNA is a screening test needing diagnostic confirmation, and cordocentesis is done later.

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 Medical genetics: prenatal diagnosis?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.