“We found no evidence that maternal smoking during pregnancy increases the risk of autism spectrum disorders,” said study leader Dr. Brian Lee, an assistant professor at Drexel University and an epidemiologist at Drexel’s School of Public Health, in collaboration with researchers from Sweden’s Karolinska Institute and the University of Bristol (Bristol, UK).
“Past studies that showed an association were most likely influenced by social and demographic factors such as income and occupation that have associations with both the likelihood of smoking and with the rate of autism spectrum disorders.”
The research team studied data from national and regional Swedish registries of 3,958 children with autism spectrum disorders, along with a control group of 38,983 children without autism born during the same period.
Overall, 19.8 percent of the children with ASD were exposed to maternal smoking during pregnancy, compared to 18.4 percent of control children.
The report helps to reassure mothers who smoked during pregnancy that their behavior was not responsible for their child’s autism, Lee said, and “crosses off another suspect on the list of possible environmental risk factors for ASD.” However, he cautioned that smoking during pregnancy is still unhealthy for mothers and has other known risks for their children.
The research is published in the Journal of Autism and Developmental Disorders.