Complications of pregnancy: locked twins: 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.

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OBG · Complications of pregnancy: locked twins

Sample item

In a twin labour the first twin presents by the breech and the second twin by the vertex. After the trunk of the first twin is delivered, the aftercoming head will not descend despite appropriate manoeuvres. What is the likely complication?

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

The answer and the reasoning

B. Locked twins

Locked twins occur when the first twin is breech and the second is cephalic, and the chins of the two fetuses become interlocked. Rarely the heads collide or become compacted. Delivery often requires caesarean, with disimpaction under anaesthesia in some cases.

Option by option

  • A. Cord entanglement of the first twin

    A nuchal cord can cause tightness but does not explain a locked head with a second twin descending.

  • B. Locked twins (correct)

    Correct. This combination of presentations is the setting in which the chins lock.

  • C. Shoulder dystocia

    Shoulder dystocia concerns the shoulders of one fetus after head delivery, not the aftercoming head of a breech.

  • D. Conjoined twins

    Conjoined twins would have been recognised on antenatal scanning.

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 B, Locked twins. Locked twins occur when the first twin is breech and the second is cephalic, and the chins of the two fetuses become interlocked.

Why is "Cord entanglement of the first twin" not the answer?

A nuchal cord can cause tightness but does not explain a locked head with a second twin descending.

Why is "Shoulder dystocia" not the answer?

Shoulder dystocia concerns the shoulders of one fetus after head delivery, not the aftercoming head of a breech.

Why is "Conjoined twins" not the answer?

Conjoined twins would have been recognised on antenatal scanning.

What concept does this question test?

It tests Complications of pregnancy: locked twins in OBG. Rarely the heads collide or become compacted. Delivery often requires caesarean, with disimpaction under anaesthesia in some cases.

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 Complications of pregnancy: locked twins?

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.