This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
[{'content': 'Most teratogenic in pregnancy \nSelect and explain. \nA. Phenytoin, B. Valproate, C. Barbiturate, D. Ethosuximide', 'role': 'user'}, {'content': "Answer: B \nExplanation: Valproate is the most teratogenic, phenytoin also isn't safe. Phenobarbitone, lamotrigine, topiramate are relatively safe drugs but 4mg folic acid is required per day. Ref: KD Tripathi 8th ed.", 'role': 'assistant'}]