All women with epilepsy who are of childbearing age should be advised (preferably before conception) that the incidence of malformations in infants of mothers with epilepsy who are treated with antiepileptic drugs (AEDs) is two or three times that of infants of mothers without epilepsy. In addition, children of mothers with epilepsy, treated or untreated with AEDs, tend to have slightly more minor anomalies than do children of fathers with epilepsy or control subjects. We do not know which of the four major AEDs (phenytoin, carbamazepine, valproate, and phenobarbital) is the most teratogenic. If AED treatment cannot be avoided, the first-choice drug for the seizure type and epilepsy syndrome should be used as monotherapy at the lowest effective dose. Diet prior to conception and during organogenesis should contain adequate amounts of folate. Prenatal diagnosis of possible birth defects should be offered, and patients should be followed closely during pregnancy, labor, and puerperium. Despite the small but significant risks, more than 90% of women with epilepsy who receive AEDs during pregnancy will deliver normal children free of birth defects.