Smoking During Pregnancy May Not Be Risk Factor for Autism

Prenatal smoke exposure, autism spectrum disorders, pregnancy

The cause of autism spectrum disorders (ASD) in children isn’t yet entirely understood, but it is likely that both genetics and environmental factors are involved. Smoking during pregnancy was thought to be one of the contributing environmental factors as tobacco smoke is associated to behavioral disorders and obstetric complications, but researchers at Drexel University find no such link in their recent study published in the Journal of Autism and Developmental Disorders.


Dr. Brian Lee, an epidemiologist and assistant professor at Drexel, who collaborated with researchers from Sweden’s Karolinska Institute and the UK’s University of Bristol, analyzed data from Swedish national and regional registries for almost 4,000 children with an ASD diagnosis and compared them to a control set of over 38,000 healthy children born during the same period.

Overall, those children that were exposed to maternal smoking during pregnancy had a slightly greater risk of being born with autism – 19.8% vs. 18.4%. However, when sociodemographic factors such as parents’ income level, education and occupation were taken into account, the association disappeared.

“Past studies that showed an association (between prenatal smoking and autism) 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,” says Dr. Lee.

While the link between autism and prenatal smoking may now be in question, there are still many other health reasons for cessation. Smoking during pregnancy exposes the fetus to dangerous chemicals such as nicotine, carbon monoxide and tar which can reduce the amount of oxygen the baby receives in utero. Babies born to smoking women are more likely to be underweight or born prematurely – other factors that have been associated in studies to be linked to an increased risk of autism.


Another recent study finds that smoking while pregnant increases the risk of disturbing early neurological development. Researchers with the University of Iowa’s College of Public Health find that smoking may cause as much as a 40% increase in the chance of developmental problems between the ages of 3 months and 2 years.

In addition, women who smoke during pregnancy are more likely to experience an etopic pregnancy, placental abruption, placenta previa, or stillbirth. And babies have a greater risk of birth defects such as cleft lip and palate.

Secondhand smoke also causes risks, such as an increased incidence of Sudden Infant Death Syndrome or respiratory conditions including asthma, bronchitis, and pneumonia.

Source Reference:
Lee, B.K., Gardner, R.M., Dal, H., Svensson, A., Galanti, M.R., Rai, D., Dalman, C., & Magnusson, C. Brief Report: Maternal Smoking During Pregnancy and Autism Spectrum Disorders. J Autism Dev Disord. DOI: 10.1007/s10803-011-1425-4

Additional Resources:
Wheby GL, Prater K, et al. “The Impact of Maternal Smoking during Pregnancy on Early Child Neurodevelopment” Journal of Human Capital, Vol 5, No 2, Summer 2011 DOI: 10.1086/660885
March of Dimes, “Smoking During Pregnancy” Accessed January 16, 2012


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