A study by researchers at Yale University injected about 335 unborn mice still in their mothers' wombs with markers to track brain development. The results showed that pregnant mice exposed to ultrasound gave birth to some offspring that suffered brain abnormalities.
When mammals develop, their brain cells multiply and neurons migrate to their proper destination in the brain, where they are then assigned a function. When environmental or genetic factors -- such as drugs or alcohol -- interfere with the process, the neurons can migrate to the wrong place in the brain, impairing brain function.
The mice exposed to ultrasound for 30 minutes or longer experienced a small but significant migration of brain neurons to improper places in the brain. The researchers say they will conduct more research on monkeys to see if the same thing happens in brains that more closely resemble that of humans.
"Those upcoming studies should give us information that will be more directly applicable to uses of ultrasound waves in humans," says lead researcher Dr. Pasko Rakic. "Ultrasound has been shown to be very beneficial in the medical context ... our study warns against its non-medical use." Rakic warns that pregnant women should not stop getting ultrasounds.
"Ultrasounds are not only potentially damaging to developing brains," added Mike Adams, a consumer health advocate, "they're also extremely loud to the fetus. Amniotic fluid is an excellent transmitter of sound energy, and ultrasounds emit powerful sound waves. The long-term effect of this unnatural exposure to extremely strong sound energy is entirely unknown," he added.