Sonography
Study Shows
Potential Dangers of Ultrasound
in Fetal Development
Aug. 24,
2006
A new study reports that
prolonged and frequent use of
ultrasound on pregnant mice
causes brain abnormalities in
the developing mouse fetus.
Researchers said that the study
findings support warnings by the
U.S. Food and Drug
Administration against the use
of medically nonindicated or
commercial prenatal ultrasound
videos.
While ultrasound generally is
considered safe if properly used
when information is needed about
a pregnancy, the FDA has
expressed concern over the
burgeoning use of the technology
for entertainment purposes, such
as in "keepsake" pictures and
videos.
There is evidence that the
exposure of pregnant mice and
nonhuman primates to ultrasound
waves may affect the behavior of
their exposed offspring.
Additionally, studies have shown
that the frequent exposure of
the human fetus to ultrasound
waves is associated with a
decrease in newborn body weight,
an increase in the frequency of
left-handedness, and delayed
speech.
Because ultrasound energy is
a high-frequency mechanical
vibration, researchers
hypothesized that it might
influence the migration of
neurons in a developing fetus.
Neurons in mammals multiply
early in fetal development and
then migrate to their final
destinations. Any interference
or disruption in the process
could result in abnormal brain
function.
In the study, researchers
injected more than 335 fetal
mice at embryonic day 16 with
special markers to track
neuronal development. Exposure
to ultrasound waves for 30
minutes or longer caused a small
but statistically significant
number of neurons to remain
scattered within inappropriate
cortical layers and in the
adjacent white matter. The
magnitude of dispersion of
labeled neurons was highly
variable but increased with
duration of exposure to
ultrasound waves.
"We have observed that a
small but significant number of
neurons in the mouse embryonic
brain do not migrate to their
proper positions in the cerebral
cortex following prolonged and
frequent exposure to
ultrasound," said Pasko Rakic,
M.D., of the Yale School of
Medicine in New Haven, Conn. The
study appeared in the Aug. 7
edition of the Proceedings of
the National Academy of
Sciences.
Dr. Rakic emphasized that the
study does not mean that
ultrasound use on human fetuses
for appropriate diagnostic and
medical purposes should be
abandoned.
"On the contrary: ultrasound
has been shown to be very
beneficial in the medical
context," he said. "Instead, our
study warns against its
non-medical use."
The research team intends to
conduct research on nonhuman
primates to see if a similar
effect is occurring in the
developing larger brains, which
are more similar to humans.
Those upcoming studies should
provide information that will be
more directly applicable to uses
of ultrasound waves in humans.
By Laurie Volkin and
Richard S. Dargan, ASRT
Contributing Writers
