Two new studies on the effects of epilepsy drugs taken during pregnancy show mixed results. The risk of birth defects with a newer drug, lamotrigine, was similar to that in women without epilepsy.
The epilepsy drug valproic acid, or sodium valproate, which has been used for a number of years, was shown to increase the risk of defects at birth. Both studies were published in the March 22 issue of Neurology, the scientific journal of the American Academy of Neurology. Another study 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 results from the study of lamotrigine is good news; lamotrigine is one of several more recent epilepsy drugs introduced after 1990 and few studies have been done on their effect on human foetuses. This study monitored birth defects in lamotrigine-exposed pregnancies reported over more than 11 years in the International Lamotrigine Pregnancy Registry.
Of 414 pregnancies where the foetus 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 increased to 12.5 percent for women who were taking lamotrigine along with valproic acid during the first trimester.
Neurologist Patricia Penovich, MD, of the Minnesota Epilepsy Group PA, in an editorial accompanying the studies, says that though a large number of women took part in the study, the number of pregnancies was too small to give absolute answers but the results are reassuring to women. The importance of controlling seizures with only one epilepsy drug if possible and of planning carefully how epilepsy drugs should used during and before pregnancy was empathised.
The news about the drug valproic acid is of course bad news; one study, which monitored 149 women found 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.
In the second study on valproic acid, British researchers recruited 163 mothers with epilepsy and their children and gave them a number of tests. A total of 249 children between the ages of 6 and 16 took the tests. The 41 children who were exposed to valproic acid during pregnancy were more likely to have low verbal IQ scores (average of 84) compared to other groups in the study, such as those exposed only to the drug phenytoin (average score of 99) or those not exposed to any epilepsy drug during pregnancy (average score of 92).
Those exposed to valproic acid were also more likely to have overall IQ scores in the extremely low, or mentally impaired, range. Two to three percent of the population would be expected to fall in this range. In the study, 22 percent of those exposed to valproic acid were in this range.