Folic Acid???
Mega-doses of folic acid are recommended for all drugs in this class, but there is a difference in the rate of birth defects from one med to another. Topamax isn't as bad as Tegretol or Depakote. The worst-case scenerio is when a woman is on two or three meds from this class. In general, Lamictal is the one least likely to cause problems.
But that does NOT mean to go off your meds! Seizures and unmedicated bipolar disorder are not good for fetuses, either. If you are taking Topamax just for migraine prophalaxis it would be worth asking your migraine doc if there is something else you could take instead.
Prescription prenatals generally have a mg of folic acid, so your total dose is 2.2 mg plus what you get from fortified foods. That's probably enough.