THURSDAY, Nov. 4 (HealthDay News) -- Teens born to women who took two or more epilepsy drugs while pregnant fared worse in school than peers with no prenatal exposure to those medications, a large Swedish study has found.

Also, teens born to epileptic mothers in general tended to score lower in several subjects, including math and English.

The findings support earlier research that linked prenatal exposure to epilepsy drugs, particularly valproic acid (brand names include Depakene and Depakote), to negative effects on a child's ability to process information, solve problems and make decisions.

"Our results suggest that exposure to several anti-epileptic drugs in utero may have a negative effect on a child's neurodevelopment," said study author Dr. Lisa Forsberg of Karolinska University Hospital.

The study was published online Nov. 4 in Epilepsia.

The study was retrospective, meaning that it looked backwards in time. Using national medical records and a study conducted by a local hospital, Forsberg and her team identified women with epilepsy who gave birth between 1973 and 1986, as well as those who used anti-epileptic drugs during pregnancy. The team then obtained records of children's school performance from a registry that provides grades for all students leaving school at 16, the age that mandatory education ends in Sweden.

The researchers identified 1,235 children born to epileptic mothers. Of those, 641 children were exposed to one anti-epileptic drug and 429 to two or more; 165 children had no known exposure to the medications.

The researchers then compared those children's school performance to that of all other children born in Sweden (more than 1.3 million) during that 13-year period.

The teens exposed to more than one anti-epileptic drug in the womb were less likely to get a final grade than those in the general population, said Forsberg. Not receiving a final grade generally means not attending general school because of mental deficits, she explained.

While teens exposed to only one anti-seizure medication did not show the same risk, they were less likely to pass with excellence. This may be the result of the influence of the anti-epileptic drug during fetal life, but it may also be the effect of factors related to epilepsy, such as genetic factors, social factors and the effect of the mother's seizures, said Forsberg. "Therefore, these data should be interpreted with caution."

Anti-epileptic medications besides valproic acid include phenytoin (such as Dilantin and Phenytek) and carbamazepine (such as Tegretol and Carbatrol). The study noted that compared to other anti-epileptic drugs, valproic acid during pregnancy seems to have a stronger negative influence on cognitive skills. However, Forsberg said that this study could not draw specific conclusions about valproic acid, since very few of the children studied were exposed to it.

There's also evidence that taking multiple anti-epileptic drugs can cause more harm than taking just one. That's why the American Academy of Neurology recommends taking just one during pregnancy, if possible, and trying medications other than valproic acid.

Dr. Jacqueline A. French, professor of neurology at NYU Langone Medical Center and director of the Clinical Trials Consortium at the NYU Comprehensive Epilepsy Center, said that the retrospective nature of the study made it difficult to control for unknowns that could have affected its findings. For example, the study could not factor in how often the mothers had seizures during their pregnancies or during critical early years of the child's life.

"I think that could have an impact on the child's development," said French. "We can't exclude the possibility that a woman on anti-epileptic drugs whose seizures are well controlled has just as much likelihood of having a child that excels as a woman who is not on the drugs."

Forsberg agreed, noting that most children exposed to anti-epileptic drugs do complete school, and that most children of epileptic mothers are born and remain healthy.

However, the study findings support current recommendations that pregnant women take just one anti-epileptic drug if possible, noted Forsberg. She also recommended that women with epilepsy plan their pregnancies. "That way, they and their doctors can come up with individual treatment plans that make the pregnancy safe for both mother and child," she said.

More information

To learn more about women and epilepsy, visit the Epilepsy Foundation.