Pregnant women who take the epilepsy drug valproate are three times more likely to have a child with an autism spectrum disorder, according to a new study published in the Journal of the American Medical Association.
Researchers analyzed data compiled from 656,000 babies born in Denmark and found that aside from other birth defects already associated with the epilepsy drug, the findings represent the "strongest evidence to date" that proves a link between the medication and autism, according to the editorial published along with the study.
And to make the study even more comprehensive, researchers accounted for other risk factors in expecting mothers, including age and health and even the health of the fathers.
"This finding isn't necessarily a brand new finding, but it's an important finding in that [researchers studied] really a much larger population, and they also looked at some other underlying driver," said Christopher Stodgell, who was not involved in the research and studies the origin of autism at the University of Rochester Medical Center.
"[Women] need to very diligent about what the effects are if they're taking valproic acid," Stodgell added.
According to the Centers for Disease Control and Prevention, about one in 88 children have an autism spectrum disorder, or ASD.
For this study, researchers analyzed a database of prescription drugs and discovered that about 6,000 mothers of the 656,000 babies tracked for the study had epilepsy, while 508 of those women used valproate during pregnancy.
And researchers report that in 2010, 4.4 percent of the children whose mother was using valproate while pregnant were diagnosed with some type of ASD.
More specifically, 2.5 percent of the children were found to have autism.
Researchers also reported that of all the babies in the study's scope, 1.5 percent had an ASD, while 0.5 percent had autism.
But Dr. Kimford Meador and David Loring from Emory University in Atlanta say that the risks and benefits associated with valproate must be further evaluated.
"Valproate is an effective drug, but it appears that is being prescribed for women of childbearing potential at a rate that does not fully consider the ratio of benefits to risks," they said in an attached editorial.
And while the link between the risk for autism and valproate is not fully understood, Jakob Christensen from Aarhus University said that it may have something to do with the development of the fetus's brain.
But Christensen also said that stopping medication prescribed to treat epilepsy could be dangerous as well.
"It's also a risk if you have seizures, both for the mother and the unborn child. [Stopping medication] is not a thing that you take lightly," Christensen said.
"Even those that are exposed to this drug, there's still a good chance-more than a 95 percent chance---that their child will never develop signs of autism."
Researchers also acknowledged that other factors, such as drinking alcohol and taking folic acid during pregnancy, were not considered for this study.
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