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Could Prenatal Ultrasounds Contribute To Cases Of Autism?

New research suggests that concerns about a possible relationship between autism and environmental exposures may be well founded.
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A conversation with Health Science Consultant, Nancy Evans:

I have known Health Science Consultant, Nancy Evans for several years through our mutual interest in women's health. Nancy is best known for her work on environmental connections to breast cancer, including the documentary film "Rachel's Daughters: Searching for the Causes of Breast Cancer." When we talked recently, she spoke passionately about her work on possible risk factors for autism. New research suggests that her concerns about environmental exposures may be well founded.

The term "autism" encompasses a group of developmental disorders characterized by an inability to communicate verbally and non-verbally with others, abnormal social behaviors, repetitive body movements, unusual attachments to objects and unusual distress when routines are changed. Within the population of children affected with autism, symptoms can range from mild to moderate to severe. Therefore, the collective term autism spectrum disorders (ASD) is often used -- particularly among the research community.

So many of us have had personal experience or have had family and friends whose child was diagnosed with this developmental disorder. Autism can be very confusing and frustrating.

What causes Autism?

Experts agree that there likely is no single cause of autism but rather a number of interacting factors that interfere with normal brain development, beginning around the time of conception and continuing throughout early childhood. Genetic factors undoubtedly contribute to the disorder but two new studies suggest that environmental factors may be equally or more important than genes. In the first study, researchers at Stanford (Hallmayer, et al) compared the incidence of autism in fraternal and identical twins and found that shared environment seemed to explain between 55 percent and 58 percent of autism cases. Genetic heritability seemed to explain only 37 percent of autism cases. Twin studies are the gold standard for studying effects of environmental exposures because twins' genetic makeup is identical (in the case of identical twins) and very similar (in fraternal twins).

In the second study, Croen and colleagues reported that antidepressant use during pregnancy was associated with a "modest" increase in the risk of autism spectrum disorders. Researchers cautioned that this one study did not prove an association between antidepressant use and autism and that more studies are needed. These new studies lend support to another expert's comment about environmental connections to autism, "... there are many factors: Chemical factors, nutritional factors, microbiological factors, physical factors like radiation and ultrasound ... I think multiple factors contribute, not just across the population, but within any one individual." (Hertz-Picciotto, 2011)

Have you a personal connection to this issue? Why are you drawn to this subject?

I have a broad-ranging interest in the connection between environmental exposures and health that evolved from my work in breast cancer. When we hear the term "environmental exposures," we think first of chemicals -- agricultural and industrial chemicals. We all bear the burden of hundreds of toxic chemicals that have invaded our bodies, sometimes before we were born. However, we also need to be aware of physical factors such as radiation and ultrasound. For the purposes of this interview, let's take a closer look at the possible connection between autism and prenatal ultrasound.

I do have a personal connection to this issue. When I heard Dr. Hertz-Picciotto mention ultrasound as a possible contributor to autism, I had just received an email from a happily pregnant young friend who reported on her most recent prenatal appointment and attached a sonogram of her developing baby. Her ecstatic comment sent chills down my spine: "Our visit was awesome! We got to watch Ryan [not his real name] for almost two hours!" While not an expert on ultrasound, I thought two hours sounded like a really long exposure -- and it is.

Ultrasound exposures longer than ten minutes can cause heating, which is clearly not good for a developing fetus, if the reason for the exposure is more vanity than medical. International guidelines suggest that exposures be as low as reasonably achievable (ALARA) to detect any problems with development. More than an hour is considered excessive. The more I learned about current prenatal ultrasound practice, the more concerned I became.

Autism was once a rare diagnosis -- How common is it now?

Today it is increasingly common, affecting one in 110 U.S. children -- one in 70 U.S. boys. And according to the Centers for Disease Control and Prevention (CDC), autism is only one of a group of developmental disabilities that is increasing in U.S. children (Boyle, et al, 2011).

Why do you think there might be a link between ultrasound and autism?

Prenatal ultrasound was once a rare medical practice, reserved for women with high-risk pregnancies. Today, prenatal ultrasound is routine for most pregnant women in developed countries. Often the first picture in the baby's photo album is the grayish sonogram taken at 16 weeks. Ultrasound has also replaced other screening methods for Down Syndrome, performing an ultrasound twice in two weeks, at a specified point in the first trimester, to assess thickness of the neck of the fetus. Results can be predictive of chromosomal abnormalities.

Apparently prenatal ultrasound also is performed many times outside of the health care system. How does this come into the equation?

I believe that this issue needs to be looked at much more closely, particularly with the increase of non-medical personnel who perform these ultrasounds. A pregnant mother's first sonogram may come from a keepsake ultrasound boutique at a local shopping mall. These boutiques have mushroomed into a huge industry. In 2004 there were 250 boutique centers ( By 2006, a single franchise operator, United Imaging Partners, had a network of 90 facilities just in the U.S. (Ostrom, 2006). Keepsake boutiques can be found in every state, including the five states that have no standards, licensure or regulatory provisions for radiologic personnel (ASRT, 2010). Take a look at the map, I find it scary!

Have states recognized this trend and prohibited any of this activity?

In 2009, Connecticut became the first state to ban keepsake ultrasounds, limiting fetal ultrasounds "to those that are ordered by a licensed health care professional and are needed for a medical or diagnostic purpose," (State of Connecticut, 2009). Similar legislation passed both houses of the California legislature in 2006, but was vetoed by then-governor Arnold Schwarzenegger.

I have been acutely aware of the recent trend of conservative legislators trying to force pregnant women to get ultrasounds.

Yes, that is correct. Arizona, Oklahoma and Texas have passed laws mandating that any woman who is planning to have an abortion first have an ultrasound procedure, during which she is shown the screen and hears a description of the fetus.

Ultrasound machines are also used in anti-choice "pregnancy crisis centers" to discourage adolescents and women with unintended pregnancies from having an abortion. Whether the sonographers in these facilities are trained and licensed is unknown. One Florida keepsake ultrasound boutique promotes its services to these organizations, claiming that a pregnant woman who "sees" her baby will be persuaded to maintain the pregnancy (Raucher, 2009).

I find the idea of compulsory ultrasound as a psychological tactic extremely disturbing and frightening.

Me too! Ironic isn't it? So what are experts saying about the research on safety of the prenatal ultrasound?

Experts question the safety of prenatal ultrasound because research shows that it affects the fetal brain and other developing body systems. "One key conclusion is the ultrasound exposure in fetal life increases the risk of left-handedness in men, suggesting that prenatal ultrasound affects the fetal brain," (Kieler, et al, 2001). Left-handedness is not bad in and of itself but it is normally rare. When left-handedness increases in a population, it indicates prenatal brain changes -- some of which may be harmful.

The issue of safety comes into question as well?

Yes. "Ultrasound is not unsound, but safety is an issue ... We do not know that modern ultrasound devices are safe ... Ultrasound operators do not know how to use the real-time display of safety information on the screen ... There is a possible link between experimental and epidemiological evidence on ultrasound and handedness," (Salvesen & Lees, 2009).

Stratmeyer and colleagues report, "Animal studies suggest that ultrasound may produce adverse effects in the neurological, immunological, hematological, developmental and genetic status of the exposed fetus," (Stratmeyer, 1982; Stratmeyer, et al, 2008).

In low-risk (uncomplicated) pregnancy, it seems to me that ultrasound does not benefit mother or baby and may cause harm. So why do we continue with ultrasound?

That's a good question, because some studies have shown that routine Doppler ultrasound in low-risk pregnancies does not benefit mother or baby. In 2000, researchers urge that future research should "address small changes in perinatal outcome and should include evaluation of ... long-term outcomes such as neurodevelopment and issues of safety," (Bricker & Neilson, 2000).

Ten years later, researchers reported the same conclusion: "Existing evidence does not provide conclusive evidence that the use of routine umbilical artery Doppler ultrasound, or combination of umbilical and uterine Doppler ultrasound in low-risk or unselected populations benefits either mother or baby. Future studies should be designed to address small changes in perinatal outcome, and should focus on potentially preventable deaths," (Alfirevic, et al, 2010). Ultrasound very early in pregnancy may carry the greatest risk. "Also, the particular sensitivity of the embryo to physical damage together with uncertainties of both risk and benefit suggest that caution should be applied to the scanning of early first trimester uncomplicated pregnancy," (Barnett, 2002).

Is it correct to say that prenatal ultrasound can heat fetal tissue and cause intense auditory effects?

Yes. Scientists at Yale (Ang, et al, 2006) found that exposure to pulsed ultrasound waves affects the movement of neurons (nerve cells) in the brains of rodents. Neurons are generated in one area of the developing brain and migrate to the cerebral cortex. This migration of neurons is one of the most delicate, complex and critical processes during fetal development. Anything that could change how and where brain cells grow and develop also may change basic brain functionality and all processes that depend on this phase of nervous system organization.

In addition, researchers at the Mayo Clinic characterized the audible effect of a typical ultrasound scanner as equal to 100 dB, equal to the sound of a subway train entering a station (Fatemi, et al, 2005).

So why the dramatic change? Has ultrasound exposure changed?

Yes! Today prenatal ultrasound exposure is used more frequently in each pregnancy and can be eight times more intense than it was 30 years ago. Most of the clinical studies establishing the safety profile of prenatal ultrasound were based on the use of machines prior to 1993 -- a watershed year in ultrasound technology and its regulation. In 1993, the Food and Drug Administration (FDA) increased the allowable output of ultrasound machines eight-fold.

At the time of this increase, FDA failed to ensure that sonographers would be appropriately trained and credentialed to use the newer machines according to recommended international guidelines.

So the FDA increased the allowable output? Was there a medical reason for this?

The FDA increased the allowable output to afford better visualization of the heart and small vessels during microsurgery, and required manufacturers to include both thermal and mechanical indexes on newer machines. However, the agency did not mandate appropriate training or require certification for operators of the equipment. FDA does not have the authority to regulate ultrasound facilities nor does it have adequate resources to regulate and inspect these facilities.

Is there a socio-economic group that is more affected by this? If so, why?

Yes. Ultrasound use and autism are more prevalent among higher socioeconomic groups.

Several studies have shown increased prevalence of autism among better-educated, more affluent communities (Durkin, et al, 2010; Van Meter, et al, 2010; Windham, et al, 2009; Maenner, et al, 2009; Fountain, et al, 2010). Women in these communities undoubtedly have health insurance and other resources to allow access to good nutrition, prenatal vitamins and excellent prenatal care, which, according to current practice, includes more ultrasound.

Are they more likely to have children with autism because they may have more frequent ultrasound exposure -- both medical and non-medical -- than women in less affluent communities who have fewer resources and less access to prenatal care?

That is a possibility that needs to be studied. Women in less affluent communities may not have the resources to go to the keepsake ultrasound boutiques, which actually could be an advantage.

So where is the biggest risk in the unregulated ultrasound boutiques?

Non-medical prenatal ultrasound is a largely unregulated industry. The FDA (2004, 2008) warned about ultrasound videos and Doppler ultrasound heartbeat monitors used "for entertainment purposes."

If the FDA warned about these facilities, why did they not regulate the training AND the decibel level?

The FDA has neither the authority nor the resources to regulate these facilities.

So how do we get the word out? If we could do one or two things, what would you suggest?

Most expectant parents have no idea that prenatal ultrasound carries any possible risk to their developing babies.

We need to make expectant parents aware that:

-The FDA warns about possible harm from non-medical sonograms.
-In uncomplicated, low-risk pregnancy, ultrasound does not benefit mother or fetus and it may cause harm.
- Some operators of ultrasound equipment may not be adequately trained in its safe use.
- Parents-to-be need to ask their OB-GYN physician why he or she recommends ultrasound, particularly early in the pregnancy. They need to be specific about WHY this, WHY now.
-Expectant parents may wish to speak to their doctor about deferring or reducing the number of ultrasound procedures as a precaution.
-Patients are required to sign consent forms prior to procedures. Consent forms for prenatal ultrasound should include information on (1) the lack of benefit in normal low-risk uncomplicated pregnancy and (2) the potential risks of the procedure to the developing baby.

What most expectant parents wish for is a healthy baby, regardless of gender or appearance. If over-exposure to ultrasound poses any threat to that outcome, who would want it?

Nancy, are there any studies being done to take a closer look at the possible connection between ultrasound and autism?

Yes, the Centers for Disease Control and Prevention (CDC) is researching this issue in their "Study to Explore Early Development (SEED)" You can check out this work at:

In the meantime, exciting as pregnancy is for the majority of expectant parents, we should think twice about the keepsake ultrasound to send off to ecstatic grandparents or to determine a child's sex. It may not be worth the risk.

Thank you, Nancy, for your passion and commitment to this issue.

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