C

Major malformations from valproate occur mainly during the first trimester; at 4 months gestation abrupt withdrawal or switching can precipitate loss of seizure control and even status epilepticus, which endangers both mother and fetus. Current guidance therefore advises continuing the same effective monotherapy during pregnancy and simply monitoring serum drug levels, rather than changing to carbamazepine (which can worsen juvenile myoclonic epilepsy) or adding/switching drugs mid-pregnancy [Battino & Tomson, 2007, PMID 18062721; Wu et al., 2016, PMID 27875769; Serafini et al., 2019, PMID 30747367].