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Carbamazepine Teratogenic Risk — MRCPsych Paper B MCQ

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HardMood DisordersCarbamazepine Teratogenic RiskMRCPsych Paper B

A 30-year-old woman with bipolar I disorder who is taking carbamazepine monotherapy requests preconception counselling. According to the MHRA review of antiseizure medicines in pregnancy, which pair of approximate absolute risks of major congenital malformations best represents carbamazepine-exposed pregnancies and the general population, respectively?

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Correct answer: B — 4–5% and 2–3%

Carbamazepine monotherapy exposure during pregnancy is associated with major congenital malformations in approximately 4–5% of pregnancies, compared with a background risk of about 2–3%; therefore B is correct. Reported abnormalities include neural tube, craniofacial, cardiac, genitourinary and skeletal defects, and risk appears dose-dependent. Approximately 10% is closer to the major-malformation risk associated with valproate, while 2–3% represents the general-population background risk rather than the carbamazepine-exposed risk. The higher estimates are not supported for carbamazepine monotherapy. In UK psychiatric practice, NICE advises against offering carbamazepine when pregnancy is planned or established and recommends discussing whether it should be stopped or changed, balancing this against relapse risk rather than stopping it without a clinical plan.

Reference: Medicines and Healthcare products Regulatory Agency, Antiepileptic drugs: review of safety of use during pregnancy, section 3.1 Carbamazepine, 2021. https://www.gov.uk/government/publications/public-assesment-report-of-antiepileptic-drugs-review-of-safety-of-use-during-pregnancy/antiepileptic-drugs-review-of-safety-of-use-during-pregnancy