Risk-benefit assessment of anticonvulsants in women of child-bearing potential.

Problems with anticonvulsants in women of child-bearing potential include potential adverse effects on appearance, contraception and pregnancy. These effects must be weighed against the overwhelming benefits of anticonvulsant treatment in the majority of women with epilepsy. Coarsened features, hirsutism and acne may occur in both men and women, particularly if they are exposed to phenytoin. Valproic acid may cause weight gain and hair loss, while carbamazepine treatment carries a significant risk of skin rashes. Anticonvulsants which are liver enzyme inducers (phenytoin, phenobarbital, primidone and carbamazepine) reduce the efficacy of the oral contraceptive pill. No 'pill failure' has been reported with valproic acid. There is a risk of increased seizure frequency in pregnancy irrespective of whether anticonvulsant treatment is taken. Individual seizures carry little risk to the mother or the fetus but status epilepticus has a significant maternal and fetal mortality. The risk of status epilepticus must be taken into account when deciding whether to stop anticonvulsant treatment before pregnancy. There is a 2 to 3 times increased malformation rate in the offspring of epileptic women on treatment. This is primarily due to the drug treatment, but epilepsy itself may also increase the malformation rate. Most malformations are mild and include facial clefts, congenital heart disease and skeletal abnormalities. Valproic acid, however, carries a 1% risk of causing neural tube defects: women receiving this drug who become pregnant should have an ultrasound and alpha-fetoprotein estimation at 16 to 18 weeks of pregnancy. If any abnormality is detected then amniocentesis should be carried out. Women with epilepsy should be counselled before conception and during pregnancy. Before achieving pregnancy a women should be on optimum treatment, preferably on one anticonvulsant. Consideration should be given to withdrawal of anticonvulsant drugs in any woman who has been seizure free for 2 years or who has only mild and infrequent seizures. Folate supplementation should be started prior to conception and should continue during pregnancy. There is a tendency for anticonvulsant drug concentrations to fall during pregnancy, and the dose may need to be increased if clinically indicated. Over 90% of epileptic women who become pregnant will have uneventful pregnancies and will produce healthy infants.