Could prenatal ultrasounds be a major contributor to the increase in autism?
This website is a repository of information related to the hypothesis, both pro and con. Over 50 papers and articles are listed and linked on the Evidence page and are referenced throughout the website.
***April 2014 – The National Institute of Environmental Health Sciences of the NIH (National Institute of Health) held a virtual forum “Autism & the Environment” on April 22, 2014. The panel of 6 experts commented on the status of research into environmental causes for autism spectrum diseases.
Why prenatal ultrasound has not been investigated as a possible cause was addressed in the last minute of the forum. It is at 55:45 on the youtube video.
For a transcript of that portion, click here.
*** There is new research in the peer-review stage which shows the behavior of lab mice adversely affected by prenatal ultrasound. Click on Key Points 8 and 50 on the Evidence page for earlier studies which have similar results. Perhaps this third study will push the burden of proof onto those who claim prenatal ultrasound is safe rather than those who say it is unsafe.***
Unsafe? Although most children appear to have had no adverse reactions to prenatal ultrasound exposure, it is possible that some fetuses are affected by factors such as genetic predisposition, operator error and machine inaccuracy. A recent study found 40% of the hospital ultrasounds tested had malfunctioning transducers.38,39 It is also possible that during certain periods of development, the brain is vulnerable to even the approved exposure levels of ultrasound.
Optional Procedure. Examination with ultrasound is optional and of little value in a normal pregnancy. Since prenatal ultrasound has never been proved safe and while research continues into the causes of increased autism, it would seem prudent to avoid such exposures.
A Summary of the Basic Facts
Autism Spectrum Disorders. Autism is most accurately known as autism spectrum disorders (ASD) because it encompasses a range of developmental disorders, most familiarly an impaired ability to communicate with others and a need for repetition. There are different levels of severity and combinations of symptoms in autism. A small percentage of cases can be linked to genetic disorders, but a recent major study of twins supports earlier studies in concluding that environmental exposures during or shortly after gestation cause a majority of autism cases.22
Neurological Effects. During brain development, cells form and migrate to the cerebral cortex. In many autism cases, brain scans reveal an increased number of cells and of minicolumns of cells. Extra minicolumns and cells can affect the brainwide connectivity pattern for communication among cells, thereby altering brain function.25,26 In one recent study, autistic children had reduced connectivity between the two sides of the brain.30 In China, fetuses scheduled for abortion were scanned. Autopsies showed those exposed to sonograms longer than 10 minutes to have significant damage.55
Ultrasound Technology. Ultrasound imaging developed from sonar used to “see” objects in the ocean. An ultrasound device for fetal imaging emits short pulses of high frequency sound waves that reflect off the tissues of the fetus. The return echoes are converted into images. In addition to vibration, ultrasound waves can cause heating of the tissue and bone.15,23,27 Therapeutic ultrasound devices actually use these effects for healing in adults.2
Evidence. A U.S. study found an apparent link between multiple second-trimester ultrasound exposure of girls and autism.12 Effects noted in two other research projects are low birth size9 and increased left-handedness.10 Animal studies show that ultrasound can both damage cells and alter their migration, creating the patterns observed in autistic brains.8 As long ago as 1995, a study on mice showed learning disabilities from relatively low exposure.50 Because the fetal skull is much thinner and more vulnerable to hyperthermic injury than the skull of an adult, any increase in fetal temperature can interfere with normal brain development.45,52 Low-birth-weight infants, who receive postnatal head ultrasounds in most hospitals, have 5 times the rate of autism spectrum diseases.34 For some exposure conditions, the thermal index (TI), as used in the FDA-approved output display standard, underestimates the extent of ultrasound-induced intracranial temperature increase.28
Matching Timelines. Twenty years ago, the FDA increased the allowable intensity of prenatal ultrasound 8-fold to improve images.23 Autism rates have risen dramatically since that time. Today, it affects 1 in 88 U.S. children, and 1 in 54 U.S. boys.40 Prenatal ultrasound was once a rare medical procedure, reserved for women with high-risk pregnancies. Prenatal ultrasound is now routine for most pregnant women in developed countries. CDC reports rate of autism in 8-year-olds rose 80% in the six-year period between 2002 and 2008. The number of ultrasounds per U.S. pregnancy rose approximately 73% between the years matching the gestation times of these age groups, 1993 and 1999.29 Every year, more women have prenatal ultrasounds and have them earlier more often during a pregnancy.29 Now, the ultrasound vaginal probe, which places the acoustic beam closer to the embryo is in common use. The children of obese mothers have a higher rate of autism.41 Their abdominal fat layer often requires more of the scans to be done with the probe.42 The prevalence of autism continues to rise.
Ultrasound Safety. The levels set by the FDA are not based on safety studies but on relative risk.4,6,14 There is essentially no evidence that prenatal ultrasounds do not damage the fetus.3,7Researchers who have touched on the topic uniformly call for closer examination of the effects of ultrasound on the fetus.1,2,5,18 Of more concern is the high rate of defects in devices in use. A Swedish study found 40% of the transducers in 676 hospital ultrasounds to be defective.38 There is widespread misunderstanding among ultrasound operators of the safety guidelines.13 Not only are there no Federal requirements for operator training, a fast-growing commercial business is keepsake ultrasound photos. Franchisers advertise that no medical background or certification is required.Ad
Call for Action
The public deserves to know immediately that there is evidence of harm. The benefits of prenatal ultrasound are minimal in normal pregnancies. Parents electing not to have ultrasounds will not impact public health. The FDA should issue an alert.
Evidence includes research reports and articles. The Key Point picks out info in the document that relates to the possibility of a relationship between fetal ultrasound and autism.
Technology explains the technology of ultrasound. There are simplified explanations and links to highly technical commentaries.
Research lists studies underway as well as research needed to further the knowledge on this topic. Also included are published studies concerning brain development abnormalities at the cellular level that can be attributed to environmental causes.
Regulations come from various governmental entities in other countries. There are a few posts but no effort to cover this topic fully. However, additional information can be submitted to be included.
Overview of Alternate Hypotheses
“The Elephant in the Room” is an overview of the topic prepared by Caroline Rodgers and presented in October 2010 to the Interagency Autism Coordinating Committee of the US Department of Health and Human Services. This succinct presentation is a valuable starting place for becoming familiar with the research and hypotheses about the cause of the rise in autism and the case for investigating prenatal ultrasound as a major source.
Key Point 48 on the Evidence page is July 2012 presentation by Caroline Rodgers to the IACC. It examines the possibility that unintended thermal effects from ultrasound scans are causing autism.