Embryology: complete hydatidiform mole: 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.

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Anatomy · Embryology: complete hydatidiform mole

Sample item

A woman at 10 weeks has vaginal bleeding, a uterus larger than dates and a snowstorm appearance on ultrasound without a fetus. The villi are diffusely swollen. What is the usual karyotype?

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

The answer and the reasoning

C. 46,XX, entirely paternal in origin

A complete mole results from fertilisation of an empty ovum, which has lost its maternal nuclear DNA, by a single sperm that duplicates, so the genome is 46,XX and entirely paternal. No fetal tissue forms and the risk of choriocarcinoma is higher. A partial mole is triploid and may contain fetal parts.

Option by option

  • A. 69,XXY, with two paternal sets

    Triploidy with two paternal sets is a partial mole, which contains fetal tissue.

  • B. 46,XX, with one maternal and one paternal set

    A normal biparental karyotype produces a normal embryo.

  • C. 46,XX, entirely paternal in origin (correct)

    Correct. The empty egg and duplicated paternal genome give a complete mole.

  • D. 45,X, entirely maternal in origin

    Monosomy X with maternal origin describes Turner syndrome and not molar pregnancy.

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.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is C, 46,XX, entirely paternal in origin. A complete mole results from fertilisation of an empty ovum, which has lost its maternal nuclear DNA, by a single sperm that duplicates, so the genome is 46,XX and entirely paternal.

Why is "69,XXY, with two paternal sets" not the answer?

Triploidy with two paternal sets is a partial mole, which contains fetal tissue.

Why is "46,XX, with one maternal and one paternal set" not the answer?

A normal biparental karyotype produces a normal embryo.

Why is "45,X, entirely maternal in origin" not the answer?

Monosomy X with maternal origin describes Turner syndrome and not molar pregnancy.

What concept does this question test?

It tests Embryology: complete hydatidiform mole in Anatomy. No fetal tissue forms and the risk of choriocarcinoma is higher. A partial mole is triploid and may contain fetal parts.

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 Embryology: complete hydatidiform mole?

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.