The teratogenicity of anticonvulsant drugs.

Background: The frequency of major malformations, growth retardation, and h ypoplasia of the midface and fingers, known as anticonvulsant embryopathy, is increased in infants exposed to anticonvulsant drugs in utero. However, whether the abnormalities are caused by the maternal epilepsy itself or by exposure to anticonvulsant drugs is not known. Methods: We screened 128,049 pregnant women at delivery to identify three g roups of infants: those exposed to anticonvulsant drugs, those unexposed to anticonvulsant drugs but with a maternal history of seizures, and those un exposed to anticonvulsant drugs with no maternal history of seizures (contr ol group). The infants were examined systematically for the presence of maj or malformations, signs of hypoplasia of the midface and fingers, microceph aly, and small body size. Results: The combined frequency of anticonvulsant embryopathy was higher in 223 infants exposed to one anticonvulsant drug than in 508 control infants (20.6 percent vs. 8.5 percent; odds ratio, 2.8; 95 percent confidence inte rval, 1.1 to 9.7). The frequency was also higher in 93 infants exposed to t wo or more anticonvulsant drugs than in the controls (28.0 percent vs. 8.5 percent; odds ratio, 4.2; 95 percent confidence interval, 1.1 to 5.1). The 98 infants whose mothers had a history of epilepsy but took no anticonvulsa nt drugs during the pregnancy did not have a higher frequency of those abno rmalities than the control infants. Conclusions: A distinctive pattern of physical abnormalities in infants of mothers with epilepsy is associated with the use of anticonvulsant drugs du ring pregnancy, rather than with epilepsy itself. (N Engl J Med 2001;344:11 32-8.) Copyright (C) 2001 Massachusetts Medical Society.