Major Birth Defects After Exposure to Newer-Generation Antiepileptic Drugs

To the Editor: Since use of older-generation antiepileptic drugs in pregnancy has been associated with increased rates of malformations in the offspring, information on the safety of the newer-generation drugs has been long awaited. Ms Mølgaard-Nielsen and Dr Hviid performed a cohort study in Denmark of major birth defects after exposure to newer-generation antiepileptic drugs.¹ They concluded that “first-trimester exposure to lamotrigine, oxcarbazepine, topiramate, gabapentin, or levetiracetam compared with no exposure was not associated with an increased risk of major birth defects.” However, the number of exposed cases was low for 3 of the drugs: 108 for topiramate, 59 for gabapentin, and 58 for levetiracetam, with adjusted prevalence odds ratios showing upper limits of confidence ranging from 3.58 to nonestimable. For lamotrigine and oxcarbazepine, the number of exposures was larger and confidence limits of prevalence rates were consistent with the conclusion that exposure to these drugs “was not associated with moderate or greater risks of major birth defects like the older-generation antiepileptic drugs.” However, the authors do not report comparative data on rates of birth defects with any older-generation antiepileptic drug. The lack of data on older agents makes the results difficult to interpret.