Hi thanks for your question.
If neurosurgeon of your wife has allowed to dicontinue the sodium valporate,you can discontinue it and plan pregnancy
without any danger of teratogenic defects.The movement you discontinue the drugs,its level in blood start decreasing.
The half life of sodium valporate is between 8 and 80 hours.Drug takes four half lives to get completely excreated from body.So there will be no drug in the blood of your wife after 12 days.
You can plan pregnancy accordingly.
Hope this answers your question.