Dr. Gregory Barkley of Wayne State, chairman of the Epilepsy Foundation\'s Professional Advisory Board, commented on new evidence that two drugs used to control epilepsy, manage bipolar disorder and alleviate migraines, show a five-fold increase in the risk of major birth defects. An estimated 56 million prescriptions for anticonvulsants were filled in the United States in the last year. An estimated 12 to 15 million of them were to women of childbearing age, Barkley said. "The risk extends to a broad proportion of the population,\" he said.