The effect of pregnancy on the epilepsies: a study of 37 pregnancies

Although studies have assessed the effect of pregnancy on epilepsy, usually the types of epilepsy are not differentiated and most have not included a control group, despite the natural history of epilepsy including fluctuations in seizure frequency.

To assess the effect of pregnancy on seizure frequency and compare this with changes in seizure frequency in non-pregnant patients. In addition, the relationship between seizure frequency during pregnancy and epilepsy type, seizure frequency prior to pregnancy and duration of epilepsy will be assessed.

Seizure frequency was assessed retrospectively in 37 pregnancies from 24 women by comparing the seizure number for the nine-month period prior to pregnancy with the number during the pregnancy. An increase in frequency was defined as a 50% or greater increase in the number of seizures. Twenty-four non-pregnant women, matched for age and epilepsy type, were included to assess fluctuations in control.

In 41% of pregnant women, there was an increase in seizure frequency, in 51% no change and in 8% improvement. In the control group, 24% had an increase, 65% no change and 11% improvement. There was no correlation between seizure frequency during pregnancy and epilepsy type and seizure frequency prior to pregnancy, but those with longer duration of epilepsy were more likely to deteriorate (p < 0.05). Alterations in anticonvulsants to reduce the risk of teratogenicity was a common identifiable cause of deterioration in control.

Significant random fluctuations in epileptic control occur, but pregnancy may have a deleterious effect on epilepsy, particularly when appropriate therapy is withdrawn to reduce teratogenicity.