Does Ultrasound Cause Autism?

Does Ultrasound cause Autism?

Because we have a baby on the way, we've been getting a lot of advice...   

One bit of advice we got, a warning really, was to tell us that we are bombarding our unborn child with ultrasound, and that could lead to autism. 

Ultrasound has been around for many decades, if there were any clear dangers it would have been obvious by now.  To suddenly fear something that has been demonstrated to work safely for decades just seem silly to me.  But to be fair, if there were some sort of subtle damage being done, during an ultrasound exam, it may indeed take this long to discover it.  

So what new studies do the anti-ultrasound people have back up this claim?  Typically they don't seem to have any, they seem to rely on the fear of "what if it's true".  I imagine that, for a lot of people, that's all it would take.  However, I need to know what the evidence points to before I can make an informed decision.  So after looking around the internet at some reputable sites (like WebMD and HeathCentral) and only finding positive things being said about the safety of ultrasound, I started looking at what the anti-ultrasound websites had to say.  I found that those websites make a lot of claims, but the only actual evidence they seem to offer is that they refer back to one or two studies.  So off I went looking for those two studies.

The first study, they refer to, is a 20 year old study (See 1993 Lancet article), that seemed to have found that human fetuses, that were exposed to multiple ultrasound (in the third trimester), had a slightly lower birth weight.  However, if you actually read the article, it turns out that the weight difference that they found was 25 grams (less than one ounce), and that was the difference in the mean birth weight of the two groups.  You might be asking yourself "what does low birth weight have to do with autism anyways?".  That's a great question, birth weight shouldn't have anything to do with autism. This study seems to be sited only in order to show that ultrasound might be affecting your baby, somehow.  It's also worth noting that when anti-ultrasound websites site this study they don't bother to mention the follow-up study.  The same group that performed the first study did a follow-up on those same children, eight years later (see Lancet article).  The newer study found that there was no perceivable differences between the children of two groups.  NO DIFFERENCE!  The findings from the original study doesn't seem to have ever been confirmed by any newer studies.  The first study may only been a statistical aberration. 

The second study, that they seem to site, is a 2006 study done at Yale (you can see/hear it at 2006 NPR article).  As the research team leader (Dr. Rakic) points out, this study was done with relatively high levels of ultrasound (because of relatively small size of the mice), and for prolonged periods of time (30 minutes focused on the brain) and the effects they found were slight.  The study makes no association with any behavioral changes in the mice later on.  When evaluating a study like this, keep in mind that the damage done by sound waves is all about the dosage level, the volume.  High levels of sound can be damaging, it can damage to your hearing and it can even damage the mechanical integrity of objects (like breaking a glass).  However, low intensity sounds will never accumulate to cause that same kind of damage.   The Yale study can not be used as any evidence for the dangers of normal ultrasounds, performed for normal durations.

So, you might be asking yourself "what's the harm with just being wary of ultrasounds?"  Like with all beliefs, the harm depends on whether or not the belief is actually real, and how you act on those beliefs.  

In the case of ultrasound, there are real demonstrable benefits to using it.  If you avoid the doctor proscribed ultrasounds you risks complications, ranging from minor complications all the way up to death.  If you avoid extra (elective) ultrasounds you may only loose an extra baby picture.  Now, weigh those benefits, which are real, against the risks, which are just speculations based on nothing more than the fear of "what if". 

Also, the harm might not just come from just being wary of ultrasounds, it could come from something entirely different.  Believing in one irrational thing often leads to believing in other irrational things.  If you're going to change your behavior, about ultrasound, based on an unsubstantiated belief what other claims are you also going to act on without sufficient evidence? 

Will you be wary of cell phones because some have claimed they might cause brain cancer (I wonder what they do to fetuses)?   Are you going to move away from power poles, because some have claimed they might cause leukemia?  Will you be wary of vaccinations because some claim they might cause autism?  

"The wise man proportions their belief to the evidence" - David Hume

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