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Do Sonograms Cause Autism? A New Study

Posted Apr 19 2012 12:00am

A new paper (“Are Prenatal Ultrasound Scans Associated with the Autism Phenotype? Follow-up of a Randomised Controlled Trial” by Yonit K. Stoch, Cori J. Williams, Joanna Granich, Anna M. Hunt, Lou I. Landau, John P. Newnham and Andrew J. O. Whitehouse) takes another look at the results of a randomized trial started in 1989. Half the mothers were given one ultrasound during their pregnancy, the rest got five. This study gave a questionnaire sensitive to autism-like traits to the now-grown-up children. This is potentially more sensitive than binary (yes/no) assessment because the questionnaire has about 50 questions.

Here is the entire abstract:

An existing randomised controlled trial was used to investigate whether multiple ultrasound scans may be associated with the autism phenotype. From 2,834 single pregnancies, 1,415 were selected at random to receive ultrasound imaging and continuous wave Doppler flow studies at five points throughout pregnancy (Intensive) and 1,419 to receive a single imaging scan at 18 weeks (Regular), with further scans only as indicated on clinical grounds. There was no significant difference in the rate of Autism Spectrum Disorder between the Regular (9/1,125, 0.8 %) and Intensive (7/1,167, 0.6 %) groups, nor a difference between groups in the level of autistic-like traits in early adulthood. There is no clear link between the frequency and timing of prenatal ultrasound scans and the autism phenotype.

Parrish Hirasaki pointed out to me that when the study was done the intensity of ultrasounds was eight-fold less than now. Here’s what the paper says about this:

Technological advancements over the past two decades have led to considerable improvements in ultrasonographic capabilities, with corresponding increases in acoustic output.

Did you read that and realize the intensities have increased by a factor of eight? Neither did I. Such a big difference in intensity means the results are not serious evidence contrary to what the abstract implies against the idea that sonograms are now causing autism.

More Asked about the failure to make clear the difference in intensity, the corresponding author, Andrew Whitehouse, replied:

The parameters of the ultrasound scans were reported clearly in the Methods section, and we refer to several other articles that include a description of the USS administered in this cohort. We are also very clear in the Discussion when we state that “the current study was not designed to investigate the use of [modern] instruments”.

I disagree. So what if the parameters of the ultrasound scans were reported clearly in the Methods section? That’s not the issue. The issue is failure to make clear the huge intensity difference between the ultrasounds they studied and modern ultrasounds. Saying that “the current study was not designed to investigate the use of [modern] instruments” does not make clear at all (much less “very clear”) how much modern ultrasounds differ from the ultrasounds actually studied. Any study can put caveats like that at the end. Yet few studies are as irrelevant as this one to the question they claim (in the title, abstract and introduction) to help answer.

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