| |
|
Download
the PDF of this article
Like many things, the safety of
ultrasound depends on the level of exposure. Studies of the lower exposures
common in the 1970s and 1980s are fairly reassuring. But since 1993,
allowable exposure levels have risen dramatically, and little research
has been done on the effects of these higher doses.
Meanwhile the use
of prenatal ultrasound continues to expand in what one consumer advocate
calls “the biggest uncontrolled experiment
in history.” (1) In 2000, approximately
2.7 million women in the United States received prenatal sonograms—some
67 percent of pregnant women. (2)
When
ultrasounds provide useful medical information, such as due date
or indications of malformations, most doctors consider the risks
acceptable.
After a medical ultrasound exam, parents typically take home a
simple 2D printout showing their fetus, and such pictures have become
a
virtual ritual of pregnancy in many industrialized countries.
Now,
manufacturers are pushing hard to win acceptance for a much more
extensive new ritual: a 4D (full motion 3D) movie of the unborn
infant,
provided by “fetal portrait” studios in shopping
malls. These movies are captured on DVD using state-of-the-art
ultrasound
equipment such as the Voluson 730 made by General Electric.
A
recent General Electric TV ad bypasses doctors to promote these
videos directly to parents, saying, “When you see your
baby for the first time on the new GE 4D ultrasound system,
it really is a miracle.” (3)
Who could resist?
General Electric’s website provides links to
commercial facilities where the new technology is available. With
names like “Womb
with a View” and “Peek-a-Boo,” these
businesses advertise heavily in parents’ magazines
and on the Internet, offering a variety of packages, ranging
from a
basic 2D ultrasound
video ($75) to a deluxe package that includes a 20-minute
4D video set to music and stored on DVD, a set of wallet
photographs, and
a set of larger photographs suitable for framing ($285).
And the videos are in hot demand. Seeing their unborn baby
thrills and comforts many parents. Writes British doctor
Stuart Campbell, “Both
maternal and paternal reaction to the moving 3D image
is something we have not previously encountered. I have
seen
fathers kiss the screen
or, more appropriately, their partner’s abdomen
in an ecstasy of recognition and pleasure.” (4)
The Safety Question
But what about safety? On their websites,
providers offer sweeping assurances that using ultrasound to
view unborn
infants is
devoid of any risk. One confidently states, “Extensive
studies over 30 years have found that ultrasound
has not been shown to cause any harm
to mother or baby.” (5) Another
says flatly, “There
has never been a harmful effect shown by the use
of ultrasound. Many women
have multiple ultrasounds during pregnancy with no
negative effect on the baby.” (6) Yet
another: “Thousands
of studies have been conducted. Nothing has surfaced
yet that indicates any harmful
effects in the use of ultrasound on animals or on
humans.” (7)
Yet
even as business interests strive to reassure their
customers, government health officials and
professional
medical associations
issue warnings.
In 1999, the American Institute
of Ultrasound in Medicine (AIUM) released the following statement:
The AIUM strongly discourages the non-medical
use of ultrasound for psychosocial or entertainment
purposes. The use of
either two-dimensional
(2D) or three-dimensional (3D) ultrasound to
only view
the fetus, obtain a picture of the fetus, or
determine the fetal
gender
without a medical
indication is inappropriate and contrary to responsible
medical practice. (8)
In
February 2004, the American Food and Drug Administration
(FDA) issued the following statement:
Persons who promote,
sell or lease ultrasound equipment for making “keepsake” fetal
videos should know that FDA views this as an
unapproved use of a medical device. In addition,
those who subject individuals to ultrasound
exposure
using a diagnostic ultrasound device (a prescription
device) without a physician’s order may
be in violation of state or local laws or regulations
regarding
use
of a prescription
medical device.
(9)
Which is right,
the statements that fetal ultrasound is perfectly
safe or the cautions against it?
Why the concern
over a technology
that
has been in everyday use in doctors’ offices
for decades?
How Ultrasound Impacts Fetal Tissue
Ultrasound is a form of energy—sound waves
vibrating at approximately a hundred times the frequency of normal
sound—and
the waves can affect tissue in a variety
of ways. Heat is one effect. In
addition,
although ultrasound itself does not produce
audible noise, secondary vibrations can
produce noises
as loud as 100 decibels, causing
fetuses to move. (10) Other
effects, still poorly understood, include
tiny
bubbles in tissue (a process known as
cavitation), sheering forces within tissues,
induced
flows within fluids, and creation of minute
quantities of toxic chemicals. (11)
Ethical
restrictions preclude the direct study
of ultrasound effects on humans.
So scientists
are using animal studies as well as data
from populations of humans exposed to ultrasound in the past.
According
to one 1998 study, temperature increases of 4.5 degrees Centigrade
(8.1 degrees
Fahrenheit) were measured
in the
brain of late-gestation live guinea-pig
fetuses insonated in utero for 2
minutes by pulsed Doppler-type
ultrasound. (12) Other
guinea-pig studies have shown adverse
effects on
cell division in bone marrow following
ultrasound
exposure. (13)
In October 2004, Pasko Rakic, Chairman of the Neurobiology Department
at Yale University, announced that he and his colleagues had observed
disruption of normal migration of cells in the brains of fetal mice
following exposure to ultrasound. Rakic is now conducting a $3 million
study to see if the same effects occur in the offspring of rhesus macaque
monkeys scanned during pregnancy. In humans, such disruption is known
to be caused by certain viruses, mutations, and drugs, and it is linked
to a range of disorders including autism and learning disabilities. [14]
In
2001, a team of Polish researchers published
actual temperature readings
obtained from
an adult human
brain during ultrasound
exposure. The results showed no temperature
increase, causing the researchers
to hypothesize that the human brain enjoys
better cooling capacities than the brains
of smaller
mammals. (15) But
no one knows
whether the rapidly developing brain
of the human fetus is similarly protected
from ultrasound-induced heat. To determine
whether such heating may produce subtle
brain damage
in human populations,
scientists
have
sought to compare the health histories
of children exposed to ultrasound and
the same data for children not exposed.(16)
To date, studies of humans exposed to
ultrasound have shown the following possible
adverse
effects: growth
retardation,
dyslexia,
and delayed
speech development. (17) But
only one effect, a higher rate of left-handedness
among
boys exposed to neonatal
ultrasound,
has
been observed in at
least three separate studies.
Why Worry about Left-handed Boys?
If the only
demonstrated result of neonatal ultrasound is more left-handed boys,
why be concerned? The
answer is twofold.
First, left-handedness
is statistically linked to many cognitive
and developmental problems ranging
from learning
difficulties to autism
to epilepsy.
Second, many researchers view
a rising rate of left-handedness as the neurological
equivalent
a “canary in a coal mine,” a
suggestion that other types of minor
brain damage may also arise. According
to medical
reporter Robert Matthews, the increase
in
left-handedness associated with neonatal
ultrasound exposure
could be the result of subtle
brain damage causing people who ought
genetically to be right-handed to
become left-handed. (18)
The
left-handedness findings were based
on health data from children
whose
mothers underwent
lower-voltage
scanning in
the late 1970s
and early 1980s. But by the mid-1990s,
average exposure levels had risen
significantly. In 2003, the ECMUS
Safety Committee noted that time-averaged
values of intensity
in the most common
ultrasound
scanning mode, “are
now up to 1000 times greater than
those reported in the 1970s.” (19) Scientists
need to repeat the left-handedness
studies, as well as studies of other
possible effects, on this younger,
more intensively exposed
population. To date, such follow-up
studies have not been done. (20) Thus,
claims that “there has
never been a harmful effect shown” simply
do not apply to today’s ultrasound
equipment.
FDA Reduces Oversight While Increasing Risk Levels
A milestone came
in 1993 when the FDA raised the maximum output of
ultrasound
machines
used in obstetrics
eightfold,
from 94
up to 720
milliwatts per square centimeter.
(21) The FDA was persuaded
that operators needed greater flexibility,
especially
when confronting life-and-death
situations such as determining
blood flows in tiny
coronary arteries in the midst
of an
ongoing heart attack.
At the time
it raised the exposure ceiling, the FDA began requiring
manufacturers to add two
on-screen safety indexes.
One measures
the heating of bone or tissue;
the other “mechanical” effects,
including cavitation caused by
the expansion of gas bubbles,
sheering forces within
tissues, and
induced
flows within fluids.
The FDA
expected that a well trained
sonographer using the
on-screen
safety indexes properly
would not subject patioents
to greater
levels of ultrasound exposure
than under the previous system
of regulation.
But then the FDA failed to ensure
that sonographers are properly
trained. According
to ultrasound
experts, the
actual state
of sonographer training
is dismally inadequate. Dr. Jacques
Abramowicz, Professor of Obstetrics
and Gynecology
and Radiation at the
University of
Chicago, said, “Only
two to three percent of the population
doing ultrasound really know
what the thermal index
and the mechanical
index mean.”
Even trained
operators are confused by the
complexity of interactions
between sound waves and human
tissues, the
ways different ultrasound
modes affect exposure, and the
different responses caused in
different parts
of
the body. Bones
respond differently
than
muscles, for example.
And bone is extremely sensitive
to ultrasound heating: the skull
of
a third-trimester
fetus heats up 50
time more quickly
than
brain tissue
when exposed to ultrasound. (22) This
means that brain structures lying
close
to the
skull, such
as the pituitary
and the hypothalamus,
are
especially at risk of secondary
heating. (23)
Yet another wild
card is the difference in sensitivity
between
fetal tissue
and adult tissue: fetal
brain tissues are more
sensitive to
disturbance because of the developmental
changes taking place.
The on-screen temperature
safety indexes can give false assurance,
even when
operators are
perfectly
trained.
According to Dr.
Abramowicz, the actual amount
of tissue heating may exceed
the level
predicted
by the safety index by a factor
of 2 to 6. Thus, actual heating
may
reach a dangerous
level even
when the safety
index shows
otherwise.
Finally, researchers
cannot agree where to set the “safety baseline” for
temperature effects. Most
researchers regard a temperature rise of .5 degrees Centigrade to
be safe. But
according to John Abbott, PhD,
director of standards communication
for Philips Medical Systems, the indexes “cannot be considered
as absolute measures of anything.They
apply to the machine,
transducer
and operating condition in
use at the time. A thermal
index of 4 is more than a thermal index
of 3.
That's all.”
Acceptable Levels of Risk
Despite
the uncertainties, doctors continue to use medical
ultrasound
because the
diagnostic benefits are
believed to outweigh any
potential harm. Says Dr.
Abramowicz, “The
common rationale is that
ultrasound
has been in use for 45
years now and we haven’t
had missing arms and legs.”
In
other words, doctors accept
that there may be
risks,
but they believe
that medical
ultrasound
remains a
beneficial practice when
performed by a trained
operator for diagnostic
purposes. According to
Dr.
Joshua Copel, Professor
of Obstetrics and Gynecology
and Pediatrics
at Yale University, “It’s
impossible to prove ultrasound
is completely safe, but
if you’re getting
medically helpful information,
then the tradeoff
is reasonable.”
As
for keepsake fetal portraits,
Dr. Copel advises his patients
to steer
clear: “We don’t
know what equipment they’re
using, what the acoustic
output is, and what the
training of the personnel
is.”
Because tissue
heat increases over the
length of exposure,
well-trained
sonographers
limit
the duration
of any medical
ultrasound procedure.
But in multiple investigations
of keepsake fetal portrait
studios, FDA investigators
found patients
being exposed
to higher machine
settings for as long as
an hour in
order to obtain fetal pictures,
much longer
than is considered prudent. (24)
What Protection from the FDA?
Despite the FDA’s own findings and expressed concerns, the federal
government has recently
adopted a notably softer stance toward the practice of “keepsake” fetal
ultrasound. When keepsake portrait studios first appeared in the 1990s,
the FDA cracked down-—hard.
In 1994, the agency issued
warnings against seven
companies to stop making
videos
or face seizure,
injunction,
or other regulatory
action.
By May 1995, five of
the companies
had shut down. (25)
As
late as 1999, the FDA
continued to issue
official
warning letters,
such
as the following
to PK
Ultrasound of Coral
Springs, Florida: “…to
use the UM4A Ultrasound
System for non-diagnostic
video taping sessions
of the fetus for keepsake
videography … is
in violation of the law.”
Now,
although fetal portrait
studios are rapidly proliferating,
the
agency has stopped
issuing
any warning letters.
In response to queries,
FDA press officer Sharon
Snider said, “We’re
considering what our
options are.”
According
to “The Gray Sheet,” a
medical devices trade
publication, the FDA
changed course after
the arrival of Bush-appointee
Dan Troy as chief legal
counsel. (26) Prior
to joining the FDA, Troy
represented pharmaceutical
and tobacco companies
on legal cases against
the FDA. (27) At
the FDA, Troy issued
a new
policy requiring all
warning letters to drug
companies and medical
device manufacturers
to be approved
by his office. In the
wake of the new policy,
the number of warning
letters issued by the
agency dropped by 70
percent. (28) In
November, 2004, Troy
left the FDA
after being widely criticized
for intervening on behalf
of drug companies, including
his former client Pfizer,
but
to date there is no indication
that his departure has
resulted in any shift
toward more active enforcement
of the FDA’s
policy on keepsake fetal
portraits.
Under a passive
FDA, the ultrasound industry
is
openly flouting
regulations. Despite
the official ban on
non-diagnostic use
of ultrasound equipment,
most keepsake fetal portrait
studios routinely advertise
non-diagnostic examinations.
Clearly,
there is money to be made at all levels
of
the ultrasound
food chain:
worldwide
sales
of ultrasound
equipment reached
$3.2 billion in 2004
according to one trade
association.
(29) And
that figure does
not include the incomes
of franchisers such
as Geddes
Keepsake, or mom-and-pop
keepsake portrait
studies.
Equipment sales
alone are
projected to triple
by 2009. (30) Market
researcher Harvey Klein recently noted
that for General Electric
4D technology has been
an area
of surprising
growth, helping that
company achieve an
18 percent
increase in
ultrasound equipment
sales in 2003, three
times the
6 percent
average
growth for other manufacturers.
(31)
Social Agendas Complicate the Safety Discussion
The biggest wildcard
in the politics of
ultrasound — even
bigger than big money — is
the anti-abortion
movement’s
embrace of the technology.
Calling the images
a “miracle,” activist
newsletters and magazines
abound in reports
of women who change
their
minds about
abortion after
seeing
3D videos of their
unborn fetus.
In
2003, Congressman
Clifford Stearns
(Republican from
Florida) introduced
the “Informed
Consent Act,” which
would subsidize ultrasound
equipment for anti-abortion “crisis
pregnancy counseling” centers.
If passed, the law
would provide up
to 50 percent
of the cost of ultrasound
equipment
for such
centers, and would
also require that
all pregnant
women be shown images
of their unborn fetus.
Has abortion politics
played a role in
the FDA’s shift
toward a passive
enforcement stance?
Neither FDA officials
nor business leaders
are willing to answer
the question on the
record. “Off
the record, I don’t
doubt it for a minute,” said
one expert.
We've Seen This Before
Some observers compare
the fetal portrait
fad to earlier
crazes
involving “perfectly
safe” imaging
technologies
and the natural
desire to look
inside the human
body. Beginning
in the 1920s,
a device known
as the “shoe-fitting
fluoroscope” was
a common feature
in shoe stores,
displaying x-ray
images of customers’ feet.
Despite decades
of warnings by
medical
professionals
and increasing
attempts by regulatory
agencies to stop
the practice,
shoe-fitting
fluoroscopes
remained popular
until the early
1960s. (32)
A Gap in the Safety Net
At the center of the fetal
portrait fad are the simple, normal desires of expectant parents
to be reassured about the health and well being
of their new baby. Sadly, that very desire for reassurance and
enjoyment makes parents vulnerable to sales pitches for technologies
whose
safety remains uncertain. Ultrasound, of course, plays a vital
role when needed for a legitimate medical purpose. But as with any
powerful
technology, caution is advised. Says Dr. Abramowicz: “I recommend
against keepsake ultrasounds. The principle is simple. You should
not use a medical device for a non-medical purpose.”
Meanwhile,
the issue of prenatal ultrasound has highlighted a serious gap
in the regulatory system. Unlike new drugs, medical devices are
not subjected to rigorous animal and human testing prior to being
released. While it is reassuring that researchers are finally
beginning to understand
just how ultrasound may affect brain development, the best time
for such research would have been before the FDA loosened the ceilings
on ultrasound exposure. Since 1993, when the rules were changed,
some 28 million pregnant women have been exposed to ultrasound.
Concerned
citizens should push for full enforcement of the FDA’s
existing rules on ultrasound, so that prenatal ultrasound is limited
to appropriate medical uses. But action needs to go further than
that. The approval process needs to be changed so that medical devices,
including
the new higher intensity ultrasound machines, are fully tested
before – not
after – being put into widespread use.
Notes and Links
1. 1993 statement attributed to UK consumer activist Beverly Beech
in Sarah Buckley, “Ultrasound Scans: Cause for Concern,” Nexus,
Vol. 9, No. 6, Oct.-Nov. 2002.
2. Figures are for the year 2000. Source: National Center of Health
Statistics of the Centers for Disease Control and Prevention, “Live
births to mothers with selected obstetric procedures,” National
Vital Statistics Reports, Vol. 50, No. 5, Feb. 12, 2002, Table 36.
3. www.gehealthcare.com/usen/ultrasound/4d/commercial.html
4. Stuart Campbell, “4D, or not 4D: that is the question,” Ultrasound
in Obstetrics and Gynecology, Vol. 19, No. 1, Dec. 12, 2002, 1-4.
5. www.firstlooksonogram.com/qa.htm
6. www.littlesproutimaging.com/faq.htm
7. www.geddeskeepsake.com/factsheet.html
8. www.aium.org
9. Carol Rados, “FDA cautions against ultrasound ‘keepsake’ images,” FDA
Consumer, Jan.-Feb., 2004. at www.fda.gov/fdac/features/2004/104_images.html
10. Eugenie Samuel, “Fetuses can hear ultrasound examinations,” New
Scientist, Vol. 10, No. 4, Dec. 4, 2001. Mostafa Fatemi, Paul L. Ogburn,
Jr., James F. Greenleaf, “Fetal Stimulation by Pulsed Diagnostic
Ultrasound,” Journal of Ultrasound in Medicine, Vol. 20, 2001,
883-889.
11. S.B. Barnett, “Can diagnostic ultrasound heat tissue and
cause biological effects?” In S.B. Barnett and G. Kossoff, eds.,
Safety of Diagnostic Ultrasound (Carnforth, UK: Parthenon Publishing,
1998), 30–31.
12. M.M. Horder, S.B. Barnett, G.J. Vella, M.J. Edwards, A.K.W. Wood, “Ultrasound-induced
temperature increase in the guinea pig fetal brain in utero: third-trimester
gestation.” Ultrasound in Medicine and Biology, Vol. 24, No.
5, June 1998, 1501-10; M.M. Horder, S.B. Barnett, G.J. Vella, M.J.
Edwards, A.K.W. Wood, “In vivo heating of the guinea pig fetal
brain by pulsed ultrasound and estimates of Thermal Index,” Ultrasound
in Medicine and Biology, Vol. 24, No. 5, June 1998, 1467-74.
13. S.B. Barnett, M.J. Edwards, P. Martin, “Pulsed ultrasound
induces temperature elevation and nuclear abnormalities in bone marrow
cells of guinea pig femurs.” Proceedings of the 6th World Congress
on Ultrasound Medicine, No. 3405 (Copenhagen, Denmark: WFUMB, 1991).
14. Jim Giles, “Ultrasound scans
accused of disrupting brain development,” news@nature.com, 10/27/2004
at www.nature.com.
15. Z. Mariak, J. Krejza, M. Swiercz, T. Lyson,
J. Lewko, “Human
brain temperature in vivo: lack of heating during transcranial color
Doppler US,” Journal of Neuroimaging, Vol. 11, No. 3, 2001, 308-312.
16. D. Marinac-Dabic, C.J. Krulewitch, and R.M.
Moore, Jr., “The
safety of prenatal ultrasound exposure in human subjects.” Epidemiology,
May 13, 2002 (2 Supplement): S19-22.
17. K.A. Salvesen, L.J. Vatten, S.H. Eik-Nes,
K. Hugdahl, L.S. Bakketeig, “Routine
ultrasonography in utero and subsequent handedness and neurological
development,” British Medical Journal, Vol. 307, 1993, 159-64.
H. Kieler, O. Axelsson, B. Haglund, S. Nilsson, K.A. Salvesen, “Routine
ultrasound screening in pregnancy and children’s subsequent handedness.” Early
Human Development, Vol. 50, 1998, 233-45.
18. Robert Matthews, “Ultrasound Scans
Linked to Brain Damage in Babies,” Epidemiology, Vol. 12, Dec.
2001, 618.
19. ECMUS Safety Committee, “Diagnostic
Ultrasound Exposure,” EFSMB
Newsletter, Jan. 2003.
20. Carol Rados, “FDA cautions against
ultrasound ‘keepsake’ images,” FDA
Consumer, Jan.-Feb., 2004.
21. Carol Rados, “FDA cautions against ultrasound ‘keepsake’ images,” FDA
Consumer, Jan.-Feb., 2004.
22. S.B. Barnett, “Can diagnostic ultrasound
heat tissue and cause biological effects?” In S.B. Barnett and
G. Kossoff, eds., Safety of Diagnostic Ultrasound (Carnforth, UK: Parthenon
Publishing,
1998), 28.
23. S.B. Barnett, “Sensitivity to diagnostic
ultrasound in obstetrics,” In
S.B. Barnett and G. Kossoff, eds., Safety of Diagnostic Ultrasound.
(Carnforth, UK: Parthenon Publishing, 1998), 58.
24. Carol Rados, “FDA cautions against
ultrasound ‘keepsake’ images,” FDA
Consumer, Jan.-Feb. 2004.
25. Marian Segal, “FDA Says No to ‘Premature’ Videos,” FDA
Consumer, Sept. 1995.
\26. “‘Keepsake’ Fetal Ultrasounds
Persist Despite FDA’s Dim View of Practice,” The Gray Sheet,
June 2, 2003.
27. Michael Kranish, “FDA Counsel’s
Rise Embodies US Shift,” Boston
Globe, Dec. 22, 2002.
28. James G. Dickinson, “FDA Cuts Warning
Letters by 70%,” Washington
Wrap-up; www.devicelink.com/mddi/archive/02/07/010.html.
29. National Electrical Manufacturers Association
at www.nema.org/prod/med/ultrasound/
30. According to market researcher Frost and
Sullivan, 3D ultrasound equipment sales are projected to triple from
$147.1 million in 2002
to $517.5 million in 2009. Source: “3D medical imaging will expand
in U.S. market,” Medical Imaging, Mar. 2003, at www.medicalimagingmag.com/news/2003-03.asp
31. “GE Healthcare takes the global leadership
position,” June
20, 2004, at www.4d-ultrasounds.com/ultrasounds/ge-position.htm
32. Jacalyn Duffin and Charles R. R. Hayter, “Baring
the Sole: The Rise and Fall of the Shoe-Fitting Fluoroscope,” Isis,
Vol. 91, No 2, June 2000, 260-282. A brief history of the shoe-fitting
fluoroscope
can also be found in the Oak Ridge Associated Universities Health Physics
Historical Instrumentation Collection at www.orau.org/ptp/collection/shoefittingfluor/shoe/htm
BACK
TO TOP
|
