Although maternal ingestion of antiepileptic drugs is strongly suspected of causing congenital defects, particularly oral clefts, the effect of epilepsy itself or a combined effect of drug intake and epilepsy have not been excluded as etiological factors. Very little is known about fetal oxygenation during a maternal grand mal epileptic seizure. We describe two cases in which fetal heart rate was recorded during a maternal epileptic seizure during labor. The first fetus became clearly asphyctic as judged from the fetal heart rate recording: immediately after the epileptic seizure there was a 13-minute continuous bradycardia wave with decreased short-term variability. After the bradycardia a phase of tachycardia with decreased short-term and long-term variability occurred. In the other fetus there was only a short period of bradycardia, which was followed by a phase of tachycardia and decreased short-term and long-term variability. Both fetuses were vigorous at birth 43 and 87 minutes, respectively, after the epileptic seizures of their mothers. We conclude that a maternal grand mal epileptic seizure can be ominous to the fetus. It is therefore important that epileptic seizures are controlled by optimal medication throughout pregnancy.