Lead author Amy Kalkbrenner, assistant professor in the University of Wisconsin-Milwaukee's Joseph J. Zilber School of Public Health, said those with Asperger's Disorder display significant difficulties in social interaction and repetitive patterns of behavior and interests, but they have linguistic ability.
Kalkbrenner and colleagues compared smoking data from birth certificates from 11 states to a database of children diagnosed with autism maintained.
Of the 633,989 children involved in the study born in 1992, 1994, 1996 and 1998, 3,315 were identified as having an autism spectrum disorder at age 8, Kalkbrenner said.
The researchers found 13 percent of mothers whose children were included in the study said they had smoked during their pregnancy.
"The study doesn't say for certain that smoking is a risk factor for autism," Kalkbrenner said in a statement. "But it does say that if there is an association, it's between smoking and certain types of autism," implicating the disorders on the autism spectrum that are less severe and allow children to function at a higher level.
The findings were published in the journal Environmental Health Perspectives.