Drugs in pregnancy: warfarin embryopathy: practice question

A Pharmacology 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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Pharmacology · Drugs in pregnancy: warfarin embryopathy

Sample item

A newborn has nasal hypoplasia, stippled epiphyses on radiographs and short fingers. The mother has a mechanical mitral valve and took an oral anticoagulant through the first trimester. What is the mechanism of this embryopathy?

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

The answer and the reasoning

A. Impaired carboxylation of vitamin K-dependent bone proteins

Warfarin crosses the placenta and blocks vitamin K epoxide reductase, so gamma-carboxylation of osteocalcin and other matrix proteins is impaired. Exposure at 6 to 12 weeks causes nasal hypoplasia and stippled epiphyses, and later exposure causes CNS defects and bleeding. Heparin does not cross the placenta.

Option by option

  • A. Impaired carboxylation of vitamin K-dependent bone proteins (correct)

    Correct. Warfarin impairs vitamin K-dependent carboxylation of bone and cartilage proteins.

  • B. Inhibition of dihydrofolate reductase

    Dihydrofolate reductase inhibition is the action of methotrexate and trimethoprim.

  • C. Direct inhibition of thrombin in the fetal circulation

    Direct thrombin inhibition is the action of dabigatran and argatroban, not warfarin.

  • D. Irreversible inhibition of platelet cyclo-oxygenase

    Platelet cyclo-oxygenase inhibition is the action of aspirin.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Impaired carboxylation of vitamin K-dependent bone proteins. Warfarin crosses the placenta and blocks vitamin K epoxide reductase, so gamma-carboxylation of osteocalcin and other matrix proteins is impaired.

Why is "Inhibition of dihydrofolate reductase" not the answer?

Dihydrofolate reductase inhibition is the action of methotrexate and trimethoprim.

Why is "Direct inhibition of thrombin in the fetal circulation" not the answer?

Direct thrombin inhibition is the action of dabigatran and argatroban, not warfarin.

Why is "Irreversible inhibition of platelet cyclo-oxygenase" not the answer?

Platelet cyclo-oxygenase inhibition is the action of aspirin.

What concept does this question test?

It tests Drugs in pregnancy: warfarin embryopathy in Pharmacology. Exposure at 6 to 12 weeks causes nasal hypoplasia and stippled epiphyses, and later exposure causes CNS defects and bleeding. Heparin does not cross the placenta.

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 Drugs in pregnancy: warfarin embryopathy?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.