(Cunningham, 21/e, pp 205, 213, 1009, 1012-1014.) Offspring of women with epilepsy have 2 to 3 times the risk of congenital anomalies even in the absence of anticonvulsant medications because seizures cause a transient reduction in uterine blood flow and fetal oxygenation. When anticonvulsant medications are used, pregnant women have an even greater risk of congenital malformations. It is recommended that women undergo a trial of being weaned off their medications prior to becoming pregnant. If antiseizure medications must be used, monotherapy is preferred to minimize the risk to the fetus since the incidence of fetal anomalies increases as additional anticonvulsants are consumed. Many anticonvulsants have been found to impair folate metabolism, and folate supplementation in pregnancy has been associated with a decreased incidence of congenital anomalies in epileptic women taking antiseizure medications. Fetal exposure to valproic acid has been associated with a 1 to 2% risk of spina bifida.