Valproat is the  antiepileptic drugs (AED) most associated with birth defects, according to a study recently presented at the  the 62nd Annual Meeting of the American Epilepsy Society.  Other AEDs such as lamotrigine and carbamazepine also showed an increased risk.

Last week, the U.S. Food & Drug Administration (FDA)  reminded health care providers about the increased risk of neural tube defects and other major birth defects, such as craniofacial defects and cardiovascular malformations, in babies exposed to valproate sodium products during pregnancy.  The agency advised that women only use valproate if it is essential to manage their medical condition. Women not actively planning a pregnancy should use effective contraception if they are taking valproate, as birth defect risks are particularly high during the first trimester, before many women know they are pregnant.

To compare different AEDs with incidence of  birth defects, scientists conducting the study presented at the annual meeting retrospectively analyzed data from epilepsy and pregnancy registries, including the North American Antiepileptic Drug Pregnancy Registry, the UK Epilepsy and Pregnancy Registry, the Lamotrigine Pregnancy Registry, the Finnish Drug Prescription database, the Swedish Medical Birth registry, and the Australian AED and Pregnancy Registry.

Overall, the study found that the prevalence of birth defects among babies born to women taking AEDs was about 6%, whereas the prevalence of birth defects in the general population is about 0.2%, similar to the rate among women with epilepsy who are not taking AEDs.  In addition, the analysis found that  treatment with more than one AEDs had  a higher malformation rate than monotherapy with AEDs (6.8% vs 4%).

Among children born to women in the North American registry, the highest malformation rate was associated with valproate (10.7%), followed by phenobarbital (6.5%) and lamotrigine (2.3%). The rate for lamotrigine was comparable to that of carbamazepine. In addition, valproate had a malformation rate that was about seven times higher than the external control population. Phenobarbital had a malformation rate five to six times higher than the control population. Lamotrigine and carbamazepine rates were not significantly higher than control population rates.

In the North American registry, 16 major malformations occurred in the offspring of 149 women who used valproate during pregnancy, and these malformations included neural tube defects, craniofacial defects, cardiovascular malformations and malformations involving other body systems.