What is a fetal side effect of lithium?

• A. Epstein's anomaly
• B. Neural tube defect
• C. Cardiac septal defect not specified
• D. Spina bifida

Answer: (A)

Lithium exposure during early pregnancy is most strongly linked to Ebstein's anomaly, a congenital malformation of the tricuspid valve. This defect arises when lithium interferes with tricuspid valve development between about weeks 4–8, causing the valve to be displaced toward the apex of the right ventricle and leading to atrialized tissue and tricuspid regurgitation. Because this is a characteristic fetal heart defect specifically associated with lithium, it is the best answer.

The other options describe other types of defects that are not the classic fetal effects of lithium. Spina bifida is a neural tube defect linked to folate status and other teratogens, not lithium. A general cardiac septal defect is a broad category and does not capture the specific pattern caused by lithium. Neural tube defects are not the known risk with lithium exposure. Note that the condition is Ebstein’s anomaly (often misspelled as Epstein’s), and that spelling is the one taught in most medical references.