(RxWiki News) As the search continues for environmental factors that may contribute to the increasing autism cases, researchers are looking in every nook and cranny for possible associations.
As a recent study reveals, at least smoking while pregnant appears, for the moment, to be ruled out as having a link to autism.
While a tiny association with one type of autism disorder was found, the researchers could not rule out coincidence to explain it.
"You still shouldn't smoke while pregnant."
Amy Kalkbrenner, an assistant professor in the University of Wisconsin-Milwaukee's Joseph J. Zilber School of Public Health, led the study looking into whether any link exists between autism spectrum disorders and mothers who smoke during their pregnancy.
Kalkbrenner and colleagues gathered data from the birth certificates of 633,989 children that noted whether the mother smoked during her pregnancy. The children were born in 11 states during the years 1992, 1994, 1996 and 1998.
There were a total of 3,315 from this group who were identified as having an autism spectrum disorder when they were 8 years old, based on the data from the Autism and Developmental Disabilities Monitoring Network.
Kalkbrenner's team then made calculations to compare the cases of children with autism to the children who had been exposed to tobacco smoke while they were in their mother's womb. They accounted for the mother's education level, race/ethnicity, marital status and age.
They found that 13 percent of the total group had mothers who smoked while they were pregnant, and 11 percent of the children with an autism spectrum disorder had mothers who smoked while pregnant.
There was a tiny association between mothers who smoked during pregnancy and children who had been diagnosed with "Autism Spectrum Disorder, Not Otherwise Specified," a diagnosis primarily used with higher functioning autism.
However, this association could not be considered significant because the link was so small that it's possible it was simply coincidence.
The researchers concluded that there does not appear to be any link between children who have autism and having a mother who smoked during pregnancy.
They stated that the "possibility" of a link between maternal smoking and the higher functioning autism disorders was "suggested," but determining whether there is any link there or how strong it might be would require further studies.
Currently, the evidence does not reveal that maternal smoking has any connection to a child later being diagnosed with any autism spectrum disorder.
The study was published online April 25 in the journal Environmental Health Perspectives. The research was funded primarily by the Centers for Disease Control and Prevention with some support from the National Institute of Environmental Health Sciences. The authors declared no competing interests.