SALT LAKE CITY — Physicians, parents and researchers have long wondered what causes autism spectrum disorders in children, and a new University of Utah study is getting them closer to finding an answer.
Pregnancy weight gain may have something to do with the evolution of the developmental disability, but researchers aren't to the point of advising any nutritional changes just yet.
The findings, published in the November issue of Pediatrics, "suggest that weight gain during pregnancy is not the cause of autism spectrum disorders, but rather may reflect an underlying process that it shares with autism spectrum disorders, such as abnormal hormone levels or inflammation," said Dr. Deborah Bilder, lead author of the study and an assistant professor of psychiatry at the U.
Added weight, or increased fat in the body, changes various hormone levels, thus impacting the fetal environment, the study states. As such, maternal body mass index and gestational weight gain have previously been associated with increased risk for developmental disabilities.
Data from the Utah Pregnancy Risk Assessment Monitoring System from 2000 to 2005 indicates a 19 percent rise in excessive pregnancy weight gain among Utah moms, as well a 25 percent increase in the proportion of women who were obese before pregnancy.
"Doctors have known for a long time that proper nutrition is essential to a healthy pregnancy," Bilder said, adding that pregnant women should not change their diet based on the study's results.
"Rather, this study provides one more piece for the autism puzzle that researchers are exploring," she said.
Autism spectrum disorders are neurobehavioral disorders manifest by a range of impaired social interactions, abnormal language development and stereotypic behavior and interests.
According to the most recent health department statistics, one in 63 Utah children have an autism spectrum disorder. Another study released last year by the U.S. Centers for Disease Control and Prevention suggests the risk might be even higher, estimating Utah's rate at one in 47.
Autism spectrum disorder is no longer considered a rare disorder and is now recognized in 1 percent to 2 percent of the population.
"This calls for further investigation of its underlying etiology as a public health concern," Bilder said.
The increased risk for autism correlated with prenatal maternal weight gain, she added, "may serve as an important marker for autism's underlying gestational etiology."
Using information gleaned from the Utah Department of Health's Registry of Autism and Developmental Disabilities, researchers studied 8-year-olds living in Salt Lake, Davis and Utah counties, the state's most populous.
A group of 128 children diagnosed with autism spectrum disorders were compared with a control group of 10,920 children of the same ages and genders. A second group of 288 Utah children with autism were also studied against data of their unaffected siblings, a model that allowed for unique examination of within-mother effects.
In both scenarios, pregnancy weight gain patterns obtained from birth certificate records were identified as common factors in mothers who gave birth to children born with autism spectrum disorders. Such a small, but consistent finding suggests that small changes in pregnancy weight gain and autism spectrum disorders may share the same underlying cause.
The result was not entirely unexpected by researchers.
"We hypothesize that excess pregnancy weight gain serves as a marker of gestational phenomena leading to autism spectrum disorders rather than as a direct risk factor," the study states. "Even in genetically vulnerable offspring, the proposed underlying autism spectrum disorder etiology may be mediated by potentially modifiable factors."
Researchers at the U. are working on substantiating their findings by collecting blood samples during the pregnancy of autism-related cases. If biomarkers are found showing a higher risk of the condition, the study states that "a window of clinical opportunity could emerge for this mechanism of injury to be prevented or attenuated."
Intervention, researchers believe, may span the range from maternal education and wellness programs to development of new drugs that could help counteract the effects of added weight during pregnancy.