During pregnancy, are newer antiseizure medications safer than older drugs?

They then looked at the risk of these birth defects among infants exposed to specific antiseizure medications taken during the first trimester of pregnancy and compared them to infants exposed to lamotrigine, an antiseizure medication used as the reference group.

Researchers found that the risk of major birth defects varied among medications. Valproate posed the highest risk, with major birth defects occurring in 9% of infants exposed. Phenobarbital followed at 6%. Among newer drugs, birth defects occurred in 5% of those exposed to topiramate, while the group exposed to lamotrigine had malformations in 2% of births.

When compared to those who took lamotrigine, those who took valproate had more than five times the risk of birth defects, those who took phenobarbital had nearly three times the risk, and those taking topiramate had over twice the risk.

"Our results confirm that using valproate, phenobarbital or topiramate during early pregnancy is linked to a higher chance of major birth defects in the infants when compared to lamotrigine,” Hernandez-Diaz said. “On the other hand, our results did not show an increased risk with medications like levetiracetam, oxcarbazepine, gabapentin and zonisamide. For lacosamide and pregabalin, the data wasn’t clear enough to make solid conclusions, so more research is needed."

A limitation of the study was that participants were enrolled months after conception and in most cases early losses of pregnancy were not assessed for malformations, so the number of malformations overall may have been underestimated.

Reference:

Sonia Hernandez-Diaz, Use of Antiseizure Medications Early in Pregnancy and the Risk of Major Malformations in the Newborn,Neurology, doi/10.1212/WNL.0000000000213959.