The prevalence of abnormal pregnancy outcomes in the offspring of 103 epileptic women, followed prospectively during pregnancy between 1982 and 1989, was compared with that in the previous study of 119 pregnancies by Dansky et al from the same institution. Our results have shown a significant decrease in the prevalence of major malformations, as compared with the previous study: 8.8% vs 24.1% (P < 0.01). Monotherapy was more frequent and the mean number of drugs used during pregnancy was significantly smaller in the present study. Phenytoin, phenobarbital and primidone were prescribed less frequently in the present study, whereas carbamazepine and valproic acid were used more frequently. Plasma levels of valproic acid during pregnancy were higher in mothers of malformed babies. In the present study, plasma folate levels were significantly higher, and more patients were taking folate supplements during pregnancy. In conclusion, the type and number of drugs used during pregnancy, as well as the plasma concentrations and serum folate levels, may determine the frequency of abnormal outcomes.