Cancer in children of epileptic mothers and the possible relation to maternal anticonvulsant therapy.

Cancer incidence among 3,727 offspring of women hospitalised for epilepsy in Denmark between 1933 and 1962 was evaluated in a record-linkage survey with the national cancer registry. The children were identified from hospital charts, population listings, and parish registries. For all children (born before and after their mothers' hospitalisation), no excess of cancer was found in comparison with the general population (49 observed vs 53.8 expected). Among the 2,579 children born after their mothers' first admission for epilepsy, and thus presumably exposed in utero to anticonvulsant drugs, 14 cancers were identified compared to 13.8 expected (relative risk 1.0; 95% confidence interval 0.6-1.7). Contrary to some previous reports, cancers of the brain and nervous system were not significantly increased (3 observed vs 2.2 expected). These data provide no evidence that anticonvulsant drugs are transplacental carcinogens, and indicate that overall increases in risk as high as 80% are unlikely.