Smoking during pregnancy is not directly linked to autism spectrum disorders (ASD) in children, according to a large population-based study in Sweden.
Exposure to various chemicals in the environment during pregnancy and infancy has been considered by researchers as a possible contributing factor toward the development of autism spectrum disorders.
Prenatal exposure to tobacco smoke is considered a potential link due to known associations between smoking and behavioral disorders and obstetric complications. Previous studies of maternal smoking and autism have given mixed results.
“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.”
Lee and his 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 born during the same period without an ASD diagnosis.
Overall, 19.8 percent of the children with ASD were exposed to maternal smoking during pregnancy, compared to 18.4 percent of control children. In unadjusted analysis, these numbers suggested a slight association between maternal smoking and the odds of an autism spectrum disorder.
However, the link disappeared when the analysis was adjusted for socio-demographic factors including the parents’ income level, education, and occupation.
The results reveal that smoking during pregnancy isn’t likely responsible for autism, Lee said, and “crosses off another suspect on the list of possible environmental risk factors for ASD.” He warns, however, that smoking during pregnancy is still unhealthy for mothers and has other known negative effects for their children.
The research is published in the Journal of Autism and Developmental Disorders.
Source: Drexel University