Ultrasound Exposure Unlikely to Cause Autism.

The prevalence of autism spectrum disorder has progressively increased over the past few decades, with estimates now at 1 in 68 individuals affected. Research continues to work on identifying both the genetic and environmental factors that could lead to autism spectrum disorder. One factor that has been scrutinized is prenatal ultrasounds. As the technology has advanced, the number of ultrasounds that women have during pregnancy has increased substantially during the past several decades, and some argue that the previously established guidelines are no longer applicable.

Now, a new study co-authored by School of Public Health researchers has found that the number or duration of abdominal fetal ultrasounds are not associated with future development of autism spectrum disorder (ASD).

The study was published in JAMA Pediatrics.

Ultrasounds are a vital tool used by providers to evaluate the developing fetus at different points in pregnancy. An abdominal ultrasound uses high-frequency sound waves, which are recorded and transformed into images of the fetus, the placenta, and the surrounding organs. These images are evaluated by providers to determine if normal development is taking place as well as to detect abnormalities, such as fetal brain and heart issues or problems with the placenta that could pose a risk to the mother or the fetus. The American Congress of Obstetrics and Gynecology recommends one or two ultrasounds for low-risk pregnancies; however, the number of medically necessary ultrasounds for all pregnancies, including high-risk, are determined by providers’ assessment of each woman’s risk factors and are done in order to help prevent and/or treat any complications that only an ultrasound can detect.

“To our knowledge, this is the first study of its kind to examine current ultrasonography data and quantify the data as it may relate to different developmental outcomes in children,” say lead author N. Paul Rosman, professor of neurology at the School of Medicine. “It is critical to note that this data should not be misinterpreted because an association does not prove a cause and effect.”

The study included 420 participants (328 boys, 92 girls) born to mothers who received prenatal care and delivered their baby at the same hospital. Among the participants, 107 had been diagnosed with ASD, 104 with other developmental delays, and 209 were controls with typical development. The researchers examined fetal ultrasound screenshots from the participants. They looked at number and timing of scans, duration of exposure, mean (average) strength (depth, frame rate, mechanical index, and thermal index), and time of Doppler and three- and four-dimensional imaging.

Overall, children with ASD had fewer ultrasound examinations during the first trimester compared to the control group; an average of 5.9 and 6.1 scans, respectively. Moreover, while the there was a statistically significant association between ASD and greater mean depth of ultrasound penetration compared to the control group, the researchers found no association between the number or the duration of the ultrasounds and future development of ASD.

“The association we found between the depth of ultrasound and ASD does not mean that ultrasounds cause autism; rather, it highlights the need for more research on how this type of exposure may impact fetal development,” says Rosman.

SPH co-authors included Gheorghe Doros, professor of biostatistics, and students James DoRosa and Allison Forman. Authors from MED included pediatrician Sherry Santiago and students Audrey Di Mauro and Rachel Vassar.