Women with epilepsy giving birth during 1973 to 1991 were identified by record 
linkage of Swedish health registries. Among 3,625 identified infants, 9 had 
spina bifida. A nested case-control study was performed, comparing drugs used in 
early pregnancy in the 9 cases and in 18 controls, matched for year of delivery, 
maternal age, and parity. Six of the spina bifida mothers had used carbamazepine 
and two had used valproic acid. Among the controls, 5 women used carbamazepine 
and one valproic acid. There is an apparent excess risk for spina bifida after 
use of either of these two drugs, but it is not statistically significant when 
the analysis is restricted to drug-using women. The findings support earlier 
reports in the literature of an association between carbamazepine and spina 
bifida.