Among the rest of the sample, about 0.8 percent of kids not exposed to the epilepsy drug developed autism. That would mean that if you took a group of 508 kids not exposed to the drug, about five of those would be diagnosed with the disorder, Christensen said.
The research is slated to be presented Monday at the American Epilepsy Society meeting in Baltimore.
Prior research has also raised concerns about valproic acid during pregnancy, leading the U.S. Food and Drug Administration and the American Academy of Neurology to issue warnings to women of childbearing age about valproate and other drugs in its class. A recent study in the Journal of the American Medical Association found that the offspring of women who took valproic acid during pregnancy are two to 12 times more likely to have serious births defects affecting the brain, heart and limbs.
And in a second study to be presented at the same meeting, researchers from the United States and the United Kingdom report that fetal exposure to valproic acid is associated with lower IQs at age 3 years.
For women with epilepsy of childbearing age, the increasing body of evidence that valproic acid may be dangerous to the fetus may present them with a difficult decision to make, said study author Dr. Kimford Meador, a professor of neurology at Emory University in Atlanta.
"You take all the research together, and it doesn't look like a very good drug for childbearing age," Meador said, noting that many pregnancies are unplanned.
However, for some women, valproic acid controls seizures when other medications have failed; for them, stopping the mediation when they're pregnant may not be an option, he said.
"About 15 percent of women do not respond to other drugs available, but they do respond to valproate," Meador said. "That's the difficulty -- it's not a simple yes-no thing."
Because this research
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