Autism may begin during pregnancy, according to a recent study Bloomberg News reported.

Researchers from the University of California, San Diego School of Medicine and the Allen Institute for Brain Science found that the developmental disorder begins when the brain cells fail to properly mature within the womb, Bloomberg News reported.

Their findings were published in the March 27 online edition of the New England Journal of Medicine.

"Building a baby's brain during pregnancy involves creating a cortex that contains six layers," Eric Courchesne, professor of neurosciences and director of the Autism Center of Excellence at UC San Diego, said in a statement. "We discovered focal patches of disrupted development of these cortical layers in the majority of children with autism."

Stoner created the first three-dimensional model visualizing brain locations where patches of cortex had failed to develop the normal cell-layering pattern.

For the study, researchers analyzed 25 genes in post-mortem brain tissue of children with and without autism. These included genes that serve as biomarkers for brain cell types in different layers of the cortex, genes implicated in autism and several control genes, according to a press release.

They found that in the brains of children with autism, key genetic markers were absent in the brain cells of multiple layers.

"This defect indicates that the crucial early developmental step of creating six distinct layers with specific types of brain cells - something that begins in prenatal life - had been disrupted," Courchesne said.

Their findings also suggest that the disruption of cell development in the brain probably occurred in the second and third trimesters, Courchesne told Bloomberg News.

"These patches of disorganized cortex are patches where cell types have failed to develop," he said. "This indicates this must have happened in fetal life when the brain is setting up neural cell types, neural connections and neural layers."

He said fetal brain cells are making complex connections by the second trimester. At this point, the "cortex develops into six layers, each with its own specific types of cells, assembly patterns and connections that perform unique roles in processing information," Bloomberg News reported.

As each cell develops it leaves behind a genetic marker that the researchers used to find difference in the brains of children with the disease. The undeveloped cells they found occurred in disorganized patches, "possibly showing why the disease takes so many forms," Bloomberg news reported.

Researchers said the next step is to identify the cause of the abnormalities.