B

Valproate carries the highest risk of congenital malformations and adverse neurodevelopment; guidelines advise replacing it with a safer alternative whenever feasible, even after the first trimester. Lamotrigine is effective for juvenile-myoclonic epilepsy and has a much lower teratogenic risk, so it should be initiated while valproate is slowly tapered to maintain seizure control and minimize fetal exposure [Harden et al., 2009, PMID 19507301; Tomson & Battino, 2009, PMID 19853219].