Researchers have found an increased risk of autism spectrum disorder and childhood autism in children born of mothers who are exposed to the anticonvulsant valproate during pregnancy, according to a study presented Monday.

Danish researchers, reporting Monday at the American Epilepsy Society's 65th annual meeting in Baltimore, said the relative risk of autism spectrum disorder in children of mothers on valproate monotherapy was 2.6 times that of children not exposed to antiepileptic medication in utero. The risk of childhood autism was almost five times that of children without prenatal exposure to valproate.

Lead investigator Jakob Christensen, MD, PhD, of Aarhus University Hospital in Demark, cautioned that while there appears to be a relationship between valproate and autism, women of childbearing age should not stop taking the medication without consulting their doctors.

"Stopping any anticonvulsant medication poses a serious danger," Christensen said. "Women taking valproate who are contemplating pregnancy should consult with their doctors about the possibility of transitioning to another drug, or reducing the dosage of their present medication when that isn't possible."

To arrive at their estimates, Christensen and his team searched data from several national registries. They identified children born between 1996 and 2006 and mothers with epilepsy who were taking valproate from 30 days before the day of conception to the day of birth. They then identified the children born during this period who were diagnosed with autism spectrum disorder and specifically assessed the subgroup diagnosed with childhood autism.