In pregnant women with epilepsy who are being treated with antiepileptic drugs (AEDs), careful clinical management is vital because seizure frequency can change during pregnancy, and both seizure activity and AED treatment can have consequences for the developing fetus. Complications of epilepsy and AED treatment include stillbirths, prematurity, low birth weight, major and minor malformations, and cognitive delay later in life. Certain AEDs probably have more adverse effects than others; data from prospective studies indicate that phenobarbital and valproate are associated with significant increases in major malformations, and retrospective studies show lower verbal IQs and greater need for extra assistance in school for children whose mothers received valproate during pregnancy. Monitoring of AED levels and dosage adjustment are warranted throughout pregnancy, and vitamin K(1) at a dose of 10 mg/day should be given in the last month, particularly when cytochrome P450 enzyme-inducing AEDs are being administered. In the postpartum period, breastfeeding is recommended; however, there is differential transfer of individual AEDs in breast milk, and the infant should be observed clinically. For all women of reproductive age, preconceptual counseling is important, and includes optimization of the AED regimen and advising the mother to take supplemental folic acid.