Ultrasounds don’t cause autism

Emily wrote in about an article about prenatal ultrasounds and autism: “I saw this on The Daily Beast today. Is the media trying to freak us expecting couples out or what? How big of a question is this in scientific circles or is this just sensational stuff? Sometimes I think there should be studies about how the internet causes anxiety disorders!”

A good question, and another post that I’m going to put under my new category, “guilt free parenting.”

The Daily Beast headline and tag reads: “Are Ultrasounds Causing Autism in Unborn Babies?” and “Scientists are uncovering disturbing evidence that those sneak peaks at baby could damage a developing brain.”

I wonder how all of this accumulated hysterical, sky-is-falling reporting is damaging adult brains. As Emily said, the internet seems to cause anxiety disorders, and it’s articles like this that get everyone worked up.

First: autism is a complex neurodevelopmental disorder that causes problems with communication, social interactions, and repetitive behaviors, starting very early in childhood. The best current evidence shows that whatever’s gone wrong, it’s going wrong very early in life, possibly even before babies are born. There are strong genetic influences, and there is still a lot we don’t know about what causes autism and how to best treat it.

Autism is especially scary because we’re hearing so much about it. It may be as common as 1 in 50 boys, and it seems like the incidence is rising dramatically—but a lot of that apparent increase is because of an ever-widening definition of autism, combined with efforts at early detection and what’s called “diagnostic substitution” (kids who would have once been diagnosed with mental retardation or other disorders are now diagnosed with autism.) But whether the true rates of autism are increasing or not, it’s certainly a huge problem for families and communities, and increased awareness, early detection,  and early treatment are urgently needed.

Because the causes of autism remain unclear, there’s a lot of speculation about what might be going on. If you Google “causes of autism”—and please, please don’t do that—you’ll find all kinds of speculation about toxins and parenting styles and government conspiracies and evil doctors who are eager to profit by harming children. You’ll also find a few tantalizing, genuine leads, things that might actually make sense. Those are what legitimate researchers are trying to study.

So what about ultrasounds? It is true that prenatal ultrasounds are being used more commonly, and the rise in their use generally follows the trend in the observed rise in autism over the last 20 years. But that observation, alone, doesn’t really show that one thing causes the other. After all, over the last 20 years we’ve also seen a dramatic increase in cell phones, cable television, frozen food, Oprah, personal computers, and Starbucks; we’ve also seen a decline in the prevalence of cursive handwriting, licking stamps, and the Sizzler Steakhouse chain. Are any of these connected to autism, or to each other? Maybe. Maybe not.

Is there some basic science about ultrasounds that makes a connection with autism plausible? Again, maybe-sort-of. Research on the effect of ultrasounds on developing mouse brains has shown a difference in the way brain cells move and migrate—but those studies looked at ultrasound exposures for many hours a day, and mouse brains develop much more quickly than ours do. We’ve also got much bigger brains, and much more tissue between our babies and an ultrasound probe than mice. Lab research on the effects of ultrasound on moving cells or bubbles is similarly unconvincing—something to think about, but a huge leap from there to “ultrasounds cause autism.”

Several studies have looked for any direct biological effect of fetal ultrasounds on human children. A 1978 report looked at about 1000 infants of mother who received amniocentesis, ultrasound, or neither—it found no developmental effects of ultrasounds. In 1984, a different group looked at 425 children, finding no biologically significant differences among those who were and were not exposed to diagnostic ultrasounds. There are also many studies looking at potential ill-effects of ultrasound technology for diagnostic use in babies, children, and adults—there are none caused by the ultrasound itself. For those of you who’d like even more detail, an excellent review of these and many other studies about ultrasounds and autism is here (unfortunately the full article is behind a paywall.)

So what’s The Daily Beast talking about—are scientists, as they say, uncovering “disturbing evidence”?

This is what’s actually reported in the article, in order of appearance:

  1. References to a study showing that among low-risk pregnancies, routine ultrasounds don’t improve outcomes. This is true. It’s irrelevant to the title or thesis of the article, but it’s true. Media lesson #1: if you don’t have a study to prove your point, talk about a different study that says something else entirely.
  2. Ultrasounds drive up the cost of care. Again, correct. Again, irrelevant. See point #1.
  3. Women who undergo frequent ultrasounds are more likely to have a pregnancy where the baby is found to have growth restriction. Well, this is true. It’s also true that if you look outside you’re more likely to know if it is raining. Fetal growth restriction is diagnosed by ultrasound. If you don’t look, you don’t know it’s happened. But looking outside doesn’t make it rain; and looking at an unborn baby with an ultrasound doesn’t cause the baby to be small. And, in any case, this is again irrelevant to autism. See point #1.
  4. The author of the article has written a book in part about her assertion that ultrasounds are to blame for what she calls “an astronomic rise in neurological disorders among America’s children.”
  5. The mice studies I referenced before—those come up now, several paragraphs in, the first even remotely relevant material. The lesson here: if you are a mouse, do not get seven hours of ultrasounds a day.
  6. A neurologist named Manuel Casanova shares the author’s concerns, and says he and colleagues have been testing the ultrasound-autism hypothesis for three years. However, and this is important: after several technical paragraphs about his ideas, he’s uncovered zero evidence to support this claim. What he’s saying are generalities about brain development that are true, and he’s juxtaposing this against information about ultrasounds and information about autism, but he doesn’t in any way refer to any of his or anyone else’s actual research establishing a connection. These are ideas. Ideas are not evidence.

That’s it. The whole article.

Now, there is a reasonable point that I will agree with—prenatal ultrasounds do not necessarily improve the health of babies, and they’re often unnecessary. Vanity ultrasounds to take 3-D pictures of unborn babies use far more energy, and it’s not implausible that there could be ill-effects—things like this are not medical uses, and ought to be discouraged until there is definitive proof of their safety.

That being said, there is no evidence for a link between ultrasounds and autism, none whatsoever. It’s not being uncovered. It’s just not there.

Roy Benaroch is a pediatrician who blogs at The Pediatric Insider. He is also the author of Solving Health and Behavioral Problems from Birth through Preschool: A Parent’s Guide and A Guide to Getting the Best Health Care for Your Child.

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