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Autism Spectrum Disorders Health Center

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Birth Complications Linked to Autism

Study: Factors Related to Oxygen Deprivation, Fetal Growth May Be Associated With Autism

Complications Related to Autism continued...

Being born during the summer months was associated with a very slight, 14%, increase in the risk of developing autism, and researchers say they can’t explain why birth season might play a role.

Cesarean delivery was associated with a 26% increased risk. But that risk was weaker, statistically, than the other exposures identified by researchers, so they aren’t sure it’s a true association. It is likely, they say, that babies who are having trouble and under stress are simply more likely to be delivered by C-section, which could explain the trend.

Factors not associated with autism risk included the use of anesthesia during delivery, assisted vaginal delivery, being born late, high birth weights, or the size of a baby’s head.

Study May Guide Future Research

“I think that we are just beginning to appreciate the potential role of events in-utero on autism risk,” says Linda Dodds, PhD, professor and director of research in the department of obstetrics and gynecology at Dalhousie University in Halifax, Nova Scotia, Canada.

Dodds has studied maternal and fetal risk factors for autism, but she was not involved in the current research.

“I think this meta-analysis was very good,” Dodds says in an email to WebMD.

She says papers like this are very helpful to researchers who are searching for the origins of such a complex disease, but they don’t tell the whole story.

“I think it is important to note that because a factor is associated with increased risk, it does not necessarily mean it causes autism,” Dodds says. “These factors may contribute to fetal growth or the overall wellbeing of the fetus and are therefore, possible markers for some underlying, yet still unidentified, cause.”

Kyle Steinman, MD, medical director of the University of Washington’s Autism Center in Seattle, says that by pooling data from previous studies, the new analysis clarifies which maternal and fetal risks may be worth paying attention to.

He says the review also helped to identify “methodological differences between prior studies that may account for inconsistencies and that should be considered carefully in designing future epidemiologic studies.”

The study was published in the journal Pediatrics.

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