New studies show mixed results on the effects of epilepsy drugs taken during pregnancy. With a newer drug, lamotrigine, the risk of birth defects was similar to that in women without epilepsy. But long-time epilepsy drug valproic acid, or sodium valproate, does increase the risk of birth defects. Both studies were published in the March 22 issue of Neurology, the scientific journal of the American Academy of Neurology.
Another study in the same issue found that children ages 6 to 16 who had been exposed to valproic acid during pregnancy had lower verbal IQ scores than children exposed to other epilepsy drugs or no epilepsy drugs during pregnancy.
The good news comes from the study of lamotrigine, which is one of several newer epilepsy drugs introduced after 1990. Few studies have been done on these drugs' effects on human fetuses. This study monitored birth defects in lamotrigine-exposed pregnancies reported over more than 11 years in the International Lamotrigine Pregnancy Registry.
Among 414 pregnancies where the fetus was exposed during the first trimester to lamotrigine as the only epilepsy drug used, there were 12 cases of major birth defects. That translates to a 2.9 percent risk of having a birth defect, which is similar to the 2 to 3 percent risk in the general population. That risk jumped to 12.5 percent for women who were taking lamotrigine along with valproic acid during the first trimester.
"Even though the number of women enrolled in this study was large, the number of pregnancies is still too small to give us absolute answers," said neurologist Patricia Penovich, MD, of the Minnesota Epilepsy Group PA, who wrote an editorial accompanying the studies. "But the results can be somewhat reassuring to women. They also emphasize the importance of trying to control seizures with only one epilepsy drug if possible and the importance of planning carefully how epilepsy drugs will be used during pregnancy before the pregnancy occurs."
The bad news is about the drug valproic acid. One study monitored the rate of birth defects in infants whose mothers had taken valproic acid as their only epilepsy drug during the first trimester of pregnancy and were enrolled in the North American Antiepileptic Drug (AED) Pregnancy Registry. Of the 149 women in the study, there were 16 infants with birth defects, or 10.7 percent. The women taking valproic acid were nearly three times more likely to have an infant with a birth defect than women taking another epilepsy drug. They were more than seven times more likely to have an infant with a birth defect than women in the general population.