A Website for Exploring the Topic

1 in 54 children born in the US in 2008 has autism per CDC 2019 report.

Could prenatal ultrasounds be the main source of the rise in autism?

This website is a repository of information related to the hypothesis. Over 60 papers and articles are referenced with links throughout the website. All are listed with links on the Evidence page.

Is prenatal ultrasound safe? Nobody knows. To get better images, the allowable intensity of prenatal ultrasound was increased 8-fold in 1992 without testing for safety then or since. The American Institute of Ultrasound in Medicine (AIUM) is designated by the FDA as the regulatory body. The safety statement on the AIUM website states that the AIUM does not know if the high-intensity levels of the last 25 years are safe. Meanwhile neurological development diseases in children have risen as the number of scans per pregnancy have risen.

Experts with the National Institute of Environmental Health Sciences of the NIH have stated that epidemiological studies are needed to confirm that prenatal ultrasound is benign. The lack of enough children in the general population who were not exposed has made such research impossible.

Examination with ultrasound is optional and of little value in a normal pregnancy. Maternal blood tests are now used to confirm the absence of Down and Edward Syndrome and neural defects. This blood screening even reveals the sex of the fetus. Since prenatal ultrasound has never been proved safe and while research continues into the causes of increased rate of autism and other neurological development diseases, it would seem prudent to avoid such exposures.

Recent US Research

March 2018 – Boston University study found a link between the penetration depth of prenatal scans and ASD. The study included 107 patients with ASD, 104 control individuals with developmental delay, and 209 controls with typical development. There was significantly greater mean depth of ultrasound penetration in the ASD group compared with the developmental delay group in the first trimester and compared with the typical development group in both the first and second trimesters. (63)

September 2016 – Researchers affiliated with the University of Washington concluded in a study of autistic boys that an ultrasound scan in the first trimester correlates to more severe autism symptoms.(60) The research was prompted by an hypothesis that a trio of factors – genetically predisposed brain at a critical time in development is exposed to a stressor – was a primary cause of autism.(25) For the 2016 study, an ultrasound scan was the stressor. The first trimester was found to be a critical time. The study did not consider whether the ultrasound exposures later in a pregnancy caused the less severe autism.

Earlier Research. UC San Diego research reported in 2014 that key genetic markers were absent in the brains of children with autism indicating that the creation in gestation of six distinct layers with specific types of brain cells had been disrupted.(56)  In 2011, a major NIH (National Institute of Health) study of fraternal twins(22) concluded that something in the environment during gestation or shortly afterward is causing the autism epidemic. 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 size(9) 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)

Chinese Research
A Chinese study published in January 2015 reports significant physical effects on the brains of lab rats as well as learning and memory effects.(58) This is not new. Click on Key Points 8, 50 and 59 on the Evidence page for earlier studies dating back 20 years which have similar results. In China, fetuses scheduled for abortion were scanned. Autopsies showed those exposed to sonograms longer than 10 minutes to have significant damage.(55) There is a new book with more information on research in China. The book – 50 Human Studies, in Utero, Conducted in Modern China, Indicate Extreme Risk for Prenatal Ultrasound: A New Bibliography by Jim West.

A Summary of the Basic Facts

Autism Spectrum Disorder. Autism is most accurately known as autism spectrum disorder (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 known genetic mutations.

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)

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.(15,23,27,61) Therapeutic ultrasound devices actually use these effects for healing in adults.(2)

Male/Female. That more boys than girls are diagnosed with ASD could be attributed to differences in the functioning of the male and female brains with the female brain showing activity in several areas in instances when the male brain engages only one area. This could make the female brain more able to adapt to abnormal functioning. Additionally, there is post-natal research that shows the testosterone levels of prepubescent male mice greatly increased by exposure to ultrasound.(62)

Matching Timelines. In 1992, without testing for safety the FDA increased the allowable intensity of prenatal ultrasound 8-fold to improve images.(23) Autism rates have risen dramatically since that time. As of 2019, it affected 1 in 59 U.S. children born in 2010, and the CDC estimate continues to increase.(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. 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 and other neurological developmental issues continues to rise especially among the affluent, a group with the greatest access to prenatal care.(57)

Ultrasound Safety. As early as 1977, FDA scientists pointed out the need to study the neurological effects found in research with mammals;(64) however, the levels later 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.(3,7)Researchers 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 2009 study found 40% of the hospital ultrasounds tested had malfunctioning transducers.(38,39)  There is widespread misunderstanding among ultrasound operators of the safety guidelines.(13) Not only are there no Federal requirements for operator training, a commercial business is ultrasound photos taken in photography studios and live scans performed at baby showers. Franchisers advertise that no medical background or certification is required.(Ad)

Alternate Hypotheses

Continuous EFM. Continuous electronic fetal monitoring (EFM) during prolonged labor using Doppler ultrasound is proposed as a possible cause of the increase in neurological disabilities in a paper authored by Caroline C. Rodgers and published in Elsevier’s Medical Hypotheses Journal, December 2020. Like prenatal ultrasound scans, this exposure of the fetus to mechanical and thermal variants has not been researched for links to the developmental issues which become apparent later. The paper suggests a number of ways to investigate this hypothesis. Finding a sizeable population of children who were not subjected to continuous EFM will be possible, unlike for the ubiquitous prenatal ultrasound scans.

Environmental Suspects. For a 2010 presentation covering many of the possible environmental causes, read the slide text from the report to the Interagency Autism Coordinating Committee (IACC) of the Dept of Health & Human Services: The Elephant in the Room.

Site Contents

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.

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.