Folic acid may reduce the likelihood of congenital abnormalities by about 15% in children exposed to antiepileptic drugs (AEDs) during the first trimester of pregnancy, according to the findings of a population-based case–control study from Denmark. 

Researchers looked at congenital abnormalities at termination of pregnancy, birth, and until 3 months of age occurring in Hungarian fetuses exposed to maternal use of carbamazepine, phenobarbital, phenytoin, or primidone during the 5 to 12 weeks from the first day of the last menstrual period.  

They calculated that compared with children unexposed to AEDs and folic acid, the odds ratio of congenital abnormalities was 1.47 (95% CI, 1.13–1.90) for children exposed to AEDS but not folic acid and 1.27 (95% CI, 0.85–1.89) for children exposed to AEDs and folic acid.  

Kjaer D, Horvath-Puhó E, Christensen J, et al. Antiepileptic drug use, folic acid supplementation, and congenital abnormalities: a population-based case-control study. 

Folic acid may reduce the likelihood of congenital abnormalities by about 15% in children exposed to antiepileptic drugs (AEDs) during the first trimester of pregnancy.