Aren’t Epilepsy and the drugs for the same associated with Neural tube defects?

Aren’t Epilepsy and the drugs for the same associated with Neural tube defects ? Why is the prophylactic Folic acid 400mg for it ?

All pregnant women should be started on prophylactic folic acid in order to prevent the development of neural tube defects. Patients with epilepsy taking regular medications are at higher risk. Enzyme-inducing anticonvulsants, such as phenytoin, carbamazepine, primidone, and phenobarbital are known to decrease folate levels, and valproic acid which may interfere with folate metabolism hence they need to take higher doses of folic acid.

Thank you.