Antenatal care: dating ultrasound: 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.

Try it

OBG · Antenatal care: dating ultrasound

Sample item

Which ultrasound parameter is the most accurate for dating a pregnancy in the first trimester?

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

The answer and the reasoning

C. Crown-rump length

Crown-rump length measured between 7 and 13 weeks estimates gestational age within about 5 to 7 days. Biparietal diameter, femur length and abdominal circumference become less accurate later because of biological variation.

Option by option

  • A. Abdominal circumference

    Abdominal circumference mainly reflects growth and nutrition.

  • B. Femur length

    Femur length is used with other parameters in the second and third trimesters.

  • C. Crown-rump length (correct)

    Correct. CRL has the least biological variation in early pregnancy.

  • D. Biparietal diameter

    BPD is useful in the second trimester but less accurate than CRL for dating.

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 OBG questions

Questions about this OBG question

What is the answer to this OBG question?

The best answer is C, Crown-rump length. Crown-rump length measured between 7 and 13 weeks estimates gestational age within about 5 to 7 days.

Why is "Abdominal circumference" not the answer?

Abdominal circumference mainly reflects growth and nutrition.

Why is "Femur length" not the answer?

Femur length is used with other parameters in the second and third trimesters.

Why is "Biparietal diameter" not the answer?

BPD is useful in the second trimester but less accurate than CRL for dating.

What concept does this question test?

It tests Antenatal care: dating ultrasound in OBG. Biparietal diameter, femur length and abdominal circumference become less accurate later because of biological variation.

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 Antenatal care: dating ultrasound?

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.