The severity of symptoms of autism in males who already possess a genetic link to the condition may be associated with exposure to first-trimester diagnostic ultrasound, according to a new study published in the journal Autism Research. The study did not explore the causes of autism, but rather the variability of symptoms.
Autism (ASD) is a highly variable condition in which symptoms and severity can differ broadly between cases. The causes and factors have largely remained a mystery, though recent research efforts have been motivated by the theory that both internal (genetics, biological dysfunction, etc.) and external (environment, nutrition, etc.) factors must be involved to produce such a wide range of variability. This theory prompted researchers to look for a potential relationship between ultrasound diagnostic techniques and ASD.
Autism, Genetics, and Ultrasound Timing
Researchers tested for an association between three variables (ultrasound exposure, timing of ultrasound in the first trimester of pregnancy, and genetic predisposition to ASD) and the severity of ASD symptoms. Data was obtained from a genetic repository known as the Simon’s Simplex Collection (SSC), which included data from 2,644 families in the United States. To identify any significant differences in symptom severity, information from subjects satisfying all three variables was compared to data from those with ASD and a genetic predisposition to the condition, but no ultrasound exposure.children who have ASD, a specific genetic predisposition to ASD, and who had been exposed to ultrasound in the first trimester displayed an increased severity in two specific ASD symptom measures: a significantly lower nonverbal IQ and increased expressions of repetitive behaviors. The findings were limited to males with autism, as no significant findings were reported for females.
Atypical Findings Make Further Research Necessary
The potential role of ultrasound exposure in ASD symptom severity is not a new idea, but this may be the first case of a significant finding. A 2010 article in the Journal of Autism and Developmental Disorders describes a study of 755 children that also controlled for trimester but found no link between ASD and ultrasound exposure. The same journal published a study in 2012 with 2,834 subjects that failed to identify an effect of ultrasound on ASD.
Critics of prenatal diagnostic ultrasounds have cited the small amount of heat the ultrasound equipment emits during a scan as a cause for concern, though there is currently no concrete evidence that this is at all harmful. Currently, the Food and Drug Administration (FDA) recommends physicians only perform diagnostic ultrasounds when they are deemed medically necessary.
Because this study’s findings are not typical, researchers say further research into this association is necessary to determine any immediate risks, and there is little reason to avoid ultrasounds at this time.
- Grether, J. K., Li, S. X., Yoshida, C. K., & Croen, L. A. (2010). Antenatal ultrasound and risk of autism spectrum disorders. Journal of Autism and Developmental Disorders, 40(2), 238-245. doi:10.1007/s10803-009-0859-4
- Stoch, Y. K., Williams, C. J., Granich, J., Hunt, A. M., Landau, L. I., Newnham, J. P., & Whitehouse, A. J. (2012). Are prenatal ultrasound scans associated with the autism phenotype? Follow-up of a randomised controlled trial. Journal of Autism and Developmental Disorders, 42(12), 2693-2701. doi:10.1007/s10803-012-1526-8
- Webb, S. J., Garrison, M. M., Bernier, R., McClintic, A. M., King, B. H., & Mourad, P. D. (2016). Severity of ASD symptoms and their correlation with the presence of copy number variations and exposure to first trimester ultrasound. Autism Research. doi:10.1002/aur.1690
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