The Journal of Autism Research just published an article detailing the effects of prenatal ultrasound on mice (Autis Res Nov 18, 2013 doi 10.1002/aur.1349, Epub ahead of print). The authors of the study, all from the University of Washington, were Abbi McClintic, Bryan King, Sara Webb, and Pierre Mourad. The senior author of the study, Dr. Mourad works within the applied physics laboratory and the Department of Bioengineering of the University of Washington. He is considered a world expert on the physics and mechanisms of action of ultrasound with numerous publications on this subject available through pubmed.
Figure: Dr. Pierre Mourad has conducted research on medical acoustics for the greater part of the last decade.
Ultrasound has been extremely beneficial as a diagnostic imaging modality during pregnancy. It is used to detect possible abnormalities of fetal development, to gauge fetal growth, and determine gender. The sound waves that constitute ultrasound are also used in Doppler devices to screen the quality of the fetal heartbeat. Unfortunately the use of ultrasound is presently being abused, with vanity exams and pseudo 3D reconstructions being offered by non-medical professionals in boutiques at different mall locations. Since anybody can acquire the equipment a new craze on prenatal ultrasound baby shower parties is now a common occurrence.
Ultrasound was deregulated in the early 1990’s, in part, due to the obesity epidemic sweeping our country. The energy of ultrasound was thereby increased, almost an eightfold, in order to better visualize the fetus. Conditions that promote an increase use of ultrasound are also risk factors for autism, e.g., advanced maternal age, complications during pregnancy (multiparity, threatened abortion). Many of these complications, giving rise to extremely small babies, provide an autism phenotype in a very significant number of patients.
There have been previous studies of rodents who were exposed to ultrasound during pregnancy. These studies describe deficits in learning and memory. A study coming from a world-renowned neuroscience laboratory indicates that exposure to ultrasound provides for abnormalities of neuronal migration during brain development. In previous publications we have indicated similar abnormalities of neuronal migration in autism spectrum disorders. However, epidemiological studies on ultrasound have not found a link to autism spectrum disorders. The latter studies suffer from many limitations including variability in practice of ultrasound usage across providers. Due to the limitations of epidemiological studies, preliminary studies were pursued using mice and standardizing levels of exposure.
In the reported experiment exposure to ultrasound (30 minutes) occurred at embryonic day 14.5 in anesthetized animals. Control animals received a sham procedure (anesthesia without ultrasound). Measurements with a thermocouple gauged the presence of possible deleterious effects of temperature. Behavioral tests were conducted at 3-4 postnatal weeks. Ultrasound exposed pubs were significantly less interested in social interactions than sham treated pubs. In addition, those animals exposed to ultrasound showed more activity, but only in the presence of an unfamiliar mouse. The researchers performed more studies ruling out the possibility that the results were due to anxiety. Exposed juvenile mice were simply less interested in social interaction.
The authors concluded that there were significant differences in the social behavior of mice exposed to ultrasound as compared to sham treated animals. “Taken together, our results demonstrate that exposure of mice in utero to thirty minutes of dUS can cause them to exhibit autistic-like behavior, specifically social deficits and hyperactivity in social circumstances” (page 8). The authors recognize the many limitations of their study (e.g., differences among species, the size of the transducer encompasses a larger portion of the mouse as compared to the human, a significantly and proportionally larger dose used in mouse as compared to diagnostic ultrasound in humans) but the results certainly warrant further explorations.
For those looking for more information on the possible effect of ultrasound during pregnancy please read one of my previous blogs where I provide many interesting references (see: http://bit.ly/VqMDq10 ). The putative relationship to autism is discussed during an interview that I had with Jennifer Margulis (see: http://bit.ly/11gIure ). Please be sure to like the Facebook page: Fetal Sonograms Safe? (see: https://www.facebook.com/WeNeedSaferSonography). The Facebook page provides the links to several informative YouTube videos.