Maternal Exposure to Air Pollution During Pregnancy Linked to Increased Autism Risk

Industrial SmokestackThe causes of autism are complex and myriad. Previous research has implicated air pollution as a contributing factor to the disorder. Now a new study published in the journal Environmental Health Perspectives adds to the evidence with the conclusion that children born to mothers living in areas with high levels of fine particulate matter during pregnancy have a significantly increased risk of autism compared to children born to mothers living in areas with low levels of fine particulate matter.

Autism spectrum disorder (ASD) is a developmental disorder that manifests during the first three years of life. The disorder is characterized by impaired social interaction and verbal and non-verbal communication and by restricted, repetitive, or stereotyped behavior. ASD affects one in 68 children in the United States.

For the present study, researchers including senior author Marc Weisskopf, associate professor of environmental and occupational epidemiology at Harvard School of Public Health in Boston, Massachusetts investigated the association between maternal exposure to air pollution during pregnancy and the risk of autism in a child.

The researchers used a nested case-control study of participants in the Nurses’ Health Study

II (NHS II), a prospective cohort of 116,430 female nurses in the United States recruited in 1989, followed by biennial mailed questionnaires. The children in the study were children born to the NHS II participants between 1990 and 2002.

Of the total number of children in the study who had been randomly selected using frequency matching for birth years, 245 had been diagnosed with ASD and 1,522 did not have an ASD diagnosis..

To determine levels of air pollution exposure before, during, and after pregnancy based on the location of the participants, the researchers used data from the US Environmental Protection Agency and other sources.

According to the study, mothers exposed to high levels of air pollution during pregnancy, especially during the third trimester, were almost twice as likely to have a child with autism compared to mothers exposed to low levels.

Additionally, the risk of autism increased as the level of exposure increased.

The researchers did not find an association between exposure to air pollution before or after pregnancy and autism risk.

Comments Weisskopf on the findings:

“Our data add additional important support to the hypothesis that maternal exposure to air pollution contributes to the risk of autism spectrum disorders. The specificity of our findings for the pregnancy period, and third trimester in particular, rules out many other possible explanations for these findings.”

Adds Weisskopf:

“The evidence base for a role for maternal exposure to air pollution increasing the risk of autism spectrum disorders is becoming quite strong. This not only gives us important insight as we continue to pursue the origins of autism spectrum disorders, but as a modifiable exposure, opens the door to thinking about possible preventative measures.”

Another recent study found that mothers of children diagnosed with autism spectrum disorder (ASD) were more than twice as likely to have suffered from preeclampsia during pregnancy than mothers of children without the disorder.


Autism spectrum disorder and particulate matter air pollution before, during, and after pregnancy: A nested case-control analysis within the Nurses’ Health Study II cohort:
Fine particulate air pollution linked with increased autism risk:
Maternal exposure to air pollution linked to offspring autism risk:

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