A 35-year-old woman on lithium for bipolar I disorder presents at 8 weeks of gestation for prenatal counselling. She has had three prior manic episodes, the most recent requiring hospitalisation. Which statement best reflects the risk-benefit discussion regarding lithium continuation?
- A Lithium must be stopped immediately as it causes a 10–20% incidence of major cardiac defects
- B Valproate is the safest alternative to lithium in the first trimester
- C Lithium is associated with a small absolute risk of Ebstein's anomaly, but discontinuation in a high-risk patient carries a substantial risk of relapse ✓
- D Lithium causes neural tube defects and should be replaced with lamotrigine at any stage of pregnancy
Correct answer: C. Lithium is associated with a small absolute risk of Ebstein's anomaly, but discontinuation in a high-risk patient carries a substantial risk of relapse
Explanation
Lithium carries a small absolute risk of Ebstein's anomaly (tricuspid valve malformation), estimated at roughly 1 in 1000 to 1 in 2000 exposed pregnancies, far lower than earlier retrospective estimates. Discontinuation of a mood stabiliser in a patient with recurrent severe bipolar disorder carries a very high risk of relapse and adverse maternal-fetal outcomes. Valproate has high teratogenicity (neural tube defects, cognitive impairment) and is generally avoided. Lamotrigine has a lower teratogenic profile but does not cause the lithium-specific anomaly.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
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