"This is an important risk factor and one that can be avoided or at least the risk reduced in women who don't need to take this and can take another drug," Dr. Kimford Meador, a professor of neurology at Emory University in Atlanta, said to Businessweek. Meador wrote an accompanying editorial published in the same journal issue. "This is the strongest evidence to date that there is a link between fetal exposure and childhood autism or autism spectrum disorder."
The Centers for Disease Control and Prevention now estimates that 1 in 50 school age children may have an autism spectrum disorder (ASD). ASDs are a group of developmental brain disorders that affect social, communication and behavioral development. The disorders can range in severity from people with milder symptoms -- called Asperger syndrome -- to those with autistic disorder or "classic" autism.
Researchers looked at 665,615 babies born in Denmark between 1996 and 2006. The children were followed for an average of 8.8 years. Out of the group, 5,437 were diagnosed with an autism spectrum disorder, and 2,067 were diagnosed with childhood autism specifically.
The researchers found that mothers of 2,644 children took anti-epileptic drugs during pregnancy, with 508 specifically taking valproate. They determined that valproate was linked to an absolute risk of 4.42 percent for an ASD and 2.5 percent for childhood autism.
For women who had epilepsy who did not take valproate, the absolute risk of having a child with an ASD was 2.44 percent, with 1.2 percent receiving a diagnosis of childhood autism.
In January 2013, a British study of 415 children also linked autism to mothers taking valproate. Those results were published in the Journal of Neurology, Neurosurgery & Psychiatry.
"Women for whom valproate is a treatment option should discuss the risks and benefits of this drug with their doctor prior to pregnancy, to ensure that their health and that of the potential child is optimized," Rebecca Bromley, a clinical psychologist and research associate at the University of Liverpool who led the British study, told HealthDay.
Image: Pregnant woman, via Shutterstock