The use of ultrasound in antenatal
care is big business, and in any big business
marketing is all-important. As a result of
decades of enthusiastic marketing, women believe
they can ensure the well-being of their babies
by reporting for an early ultrasound scan and
that early detection of a problem is beneficial
for these babies. That is not necessarily so,
and there are a number of studies which show
that early detection can be harmful.
In response to women’s
desire for information about the implications
of routine ultrasound examinations, Jean Robinson
and I wrote the book Ultrasound? Unsound, in
which we reviewed the research evidence and
drew attention to some of the hazards (Beech
and Robinson, 1996). But since then more evidence
has accumulated. For example:
It is ironic that women who have had previous
miscarriages often have additional ultrasound
examinations in order to "reassure"
them that their baby is developing properly.
Few are told of the risks of miscarriage or
premature labour or birth.
Obstetricians in Michigan (Lorenz
et al., 1990) studied fifty-seven women who
were at risk of giving birth prematurely. Half
were given a weekly ultrasound examination;
the rest had pelvic examinations. Preterm labour
was more than doubled in the ultrasound group–52
percent–compared with 25 percent in the
controls. Although the numbers were small the
difference was unlikely to have emerged by
A large randomised controlled
trial from Helsinki (Saari-Kemppainen et al.,
1990) randomly divided over 9,000 women into
a group who were scanned at sixteen to twenty
weeks compared with those who were not. It
revealed twenty miscarriages after sixteen
to twenty weeks in the screened group and none
in the controls.
A later study in London (Davies
et al., 1993) randomised 2,475 women to routine
Doppler ultrasound examination of the umbilical
and uterine arteries at nineteen to twenty-two
weeks and thirty-two weeks compared with women
who received standard care without Doppler
ultrasound. There were sixteen perinatal deaths
of normally formed infants in the Doppler group
compared with four in the standard care group.
It is not only pregnant patients
who are at risk, however. Physiotherapists
use ultrasound to treat a number of conditions.
A study done in Helsinki (Taskinen et al.,
1990) found that if the physiotherapist was
pregnant, handling ultrasound equipment for
at least twenty hours a week significantly
increased the risk of spontaneous abortion.
Also, the risk of spontaneous abortions occurring
after the tenth week was significantly increased
for deep heat therapies given for more than
five hours a week and ultrasound more than
ten hours a week.
Diagnosis of placental praevia
The Saari-Kemppainen study also revealed the
lack of value in early diagnosis of placenta
praevia. Of the 4,000 women who were scanned
at sixteen to twenty weeks, 250 were diagnosed
as having placenta praevia. When it came to
delivery, there were only four. Interestingly,
in the unscanned group there were also four
women found at delivery to have this condition.
All the women were given caesarean sections
and there was no difference in outcomes between
the babies. Indeed, there are no studies which
demonstrate that early detection of placenta
praevia improves the outcome for either the
mother or the baby. The researchers did not
investigate the possible effects on the 246
women who presumably spent their pregnancies
worrying about having to undergo a caesarean
section and the possibility of a sudden haemorrhage.
Babies with serious defects
Almost all babies receive a dose of ultrasound,
but even at the best centres wide variations
occur in detection rates for babies with major
heart abnormalities. Both national and international
detection rates differ widely in published
studies (which are usually undertaken in centres
of excellence), but the majority of mothers
will be exposed to older machines in ordinary
hospitals and clinics. The skill of the operators
will vary (everybody has to learn sometime),
but even with the best machines and the best
operators misdiagnoses occur. A study from
Oslo (Skari et al., 1998) looked at how many
babies born with serious defects had been diagnosed
by antenatal scans, and whether the early diagnosis
made any difference to the outcomes. Women
in Norway have a scan at seventeen to twenty-one
weeks done by trained midwives, who refer to
obstetricians if an abnormality is suspected.
In nineteen months, thirty-six
babies were referred from a population of 2.5
million. They had diaphragmatic hernias, abdominal
wall defects, bladder extrophy or meningomyelocele.
Only thirteen of the thirty-six defects had
been detected before birth (36 percent). They
found that only two of eight congenital diaphragmatic
hernias were picked up on ultrasound, half
the cases of abdominal wall defects (six out
of twelve), 38 percent of the meningomyelocele
(five out of thirteen) and none of the three
cases of bladder extroversion. The mothers
had an average of five scans (from one to fourteen);
those in whose cases abnormality was detected
had an average of seven.
Three out of the thirteen babies
diagnosed antenatally died. There was one death
in the twenty-three undiagnosed. All thirteen
babies with antenatal diagnosis were delivered
by caesarean. Nineteen of the twenty-three
undiagnosed babies had an uncomplicated vaginal
delivery. The diagnosed babies had lower birth
weight and two weeks shorter gestation. Although
the babies with pre-diagnosed abdominal wall
defects received surgery more quickly (four
hours versus thirteen hours), the outcomes
were the same in both groups. Although small,
this is an important study.
Pregnant women often automatically
assume that antenatal detection of serious
problems in the baby means that lives will
be saved or illness reduced. Knowing about
the problem in advance did not benefit these
babies; more of them died. They got delivered
sooner, when they were smaller, a choice that
could have long-term effects. All twelve babies
with abdominal wall defects survived. But for
the six detected on the scan, their length
of hospital stay was longer and they spent
longer on ventilators, though the numbers are
too small to be significant. They were operated
on sooner (four hours rather than thirteen
hours) but the outcomes were the same.
Growth Retarded Babies
One of the promises held out by antenatal scanning
is that obstetricians will be able to identify
the baby with problems and do something to
help it. A German study from Wiesbaden hospital
(Jahn et al., 1998) found that out of 2,378
pregnancies only fifty-eight of 183 growth
retarded babies were diagnosed before birth.
Forty-five fetuses were wrongly diagnosed as
being growth retarded when they were not. Only
twenty-eight of the seventy-two severely growth-retarded
babies were detected before birth despite the
mothers having an average of 4.7 scans.
The babies diagnosed as small
were much more likely to be delivered by caesarean
- 44.3 percent compared with 17.4 percent for
babies who were not small for dates. If the
baby actually had intrauterine growth retardation
(IUGR) the section rate varied hugely according
to whether it was diagnosed before birth (74.1
percent sectioned) or not (30.4 percent).
So what difference did diagnosis
make to the outcome for the baby? Pre-term
delivery was five times more frequent in those
whose IUGR was diagnosed before birth than
those who were not. The average diagnosed pregnancy
was two to three weeks shorter than the undiagnosed
one. The admission rate to intensive care was
three times higher for the diagnosed babies.
The long-term emotional impact
The effects of screening on both parents can
be profound. For example, women waiting for
the results of tests try not to love the baby
in case they have to part with it. The medical
literature has little to say about the human
costs of misdiagnosis unless the baby was mistakenly
aborted, and even then it tends to focus on
legal action. However, a letter in the British
Medical Journal revealed how a diagnosis of
a minor anomaly can have serious long-term
implications for the family:
A couple was referred for amniocentesis
during the wife’s second pregnancy on
the grounds of maternal age, thirty-five years,
and anxiety. Their three-year-old son played
happily during the consultation. When his wife
and son had left the room after the procedure
the husband confided that they had opted for
amniocentesis to avoid having another "brain
damaged" child. On questioning it became
apparent that an ultrasound examination before
their son’s birth had shown a choroid
plexus cyst. Despite having a healthy child,
the husband remained convinced that this cyst
could cause his son to be disabled. (Mason
and Baillie, 1997).
Evaluating the risks
When ultrasound was first developed researchers
suggested that "the possibility of hazard
should be kept under constant review"
(Donald, 1980), and they said that it would
never be used on babies under three months.
However, as soon as vaginal probe ultrasound
was developed, which could get good pictures
in early pregnancies (and get nearer to the
baby giving it a bigger dose), this initial
caution was ignored.
Research by Lieberskind revealed
"the persistence of abnormal behaviour
. . . in cells exposed to a single dose diagnostic
ultrasound ten generations after insonation."
She concluded, "If germ cells were . .
. involved, the effects might not become apparent
until the next generation" (Lieberskind,
1979). When asked what problems should be looked
for in human studies, she suggested: "Subtle
ones. I’d look for possible behavioural
changes, in reflexes, IQ, attention span"
Because ultrasound has been developed
rapidly without proper evaluation it is extremely
difficult to prove that ultrasound exposure
causes subtle effects. After all, it took over
ten years to prove that the gross abnormalities
found in some newborn babies were caused by
thalidomide. However, there are a number of
ultrasound studies which raise serious questions
that still have to be addressed.
The first evidence we saw of
possible damage to humans came in 1984 when
American obstetricians published a follow-up
study of children, aged seven to twelve years
born in three different hospitals in Florida
and Denver, who had been exposed to ultrasound
in the womb (Stark et al., 1984). Compared
with a control group of children who had not
been exposed they were more likely to have
dyslexia and to have been admitted to hospital
during their childhood, but no other differences
In 1993 a study in Calgary, Alberta
which examined the antenatal records of seventy-two
children with delayed speech of unknown cause
were compared with those of 142 controls who
were similar in sex, date of birth and birth
order within the family. The children were
similar in social class, birthweight and length
of pregnancy. The children with speech problems
were twice as likely as controls to have been
exposed to ultrasound in the womb. Sixty-one
percent of cases and only 37 percent of controls
had had at least one exposure.
A Norwegian study (Salvesen,
1993) showed an increase in left handedness,
but no increase in dyslexia. While the increase
in left handedness was not large, it does suggest
that ultrasound has an effect on the development
of the brain. It should be noted, however,
that the scanners used in this study emitted
very low doses of ultrasound–lower than
exposures from many machines nowadays–the
women had only two exposures, and it was real
time, not Doppler, a more powerful form of
Assessing the risks
"Present day ultrasonic diagnostic machines
use such small levels of energy that they would
appear to be safe, but the possibility must
never be lost sight of that there may be safety
threshold levels possibly different for different
tissues, and that with the development of more
powerful and sophisticated apparatus these
may yet be transgressed" (Donald, 1979).
Donald’s foresight was
remarkable. The machines in use today are far
more powerful than the machines used a decade
or more ago, and new variants are being developed
all the time.
There has been inadequate research
into the potential long-term effects. Measuring
the outcome of any intervention in pregnancy
is very complicated because there are so many
things to look at. Intelligence, personality,
growth, sight, hearing, susceptibility to infection,
allergies and subsequent fertility are but
a few issues which, if affected, could have
serious long-term implications, quite apart
from the numbers of babies who have a false
positive or false negative diagnosis. Because
a baby grows rapidly, exposing it to ultrasound
at eight weeks can have different effects than
exposure at, for example, ten, eighteen or
twenty-four weeks (this is one of the reasons
the effects of potential exposure are so difficult
to study). Women are now exposed to so many
different types of ultrasound: Doppler scans,
real-time imaging, triple scans, external fetal
heart-rate monitors, hand held fetal monitors.
Unlike drugs, whereby every new drug must be
tested, the rapid development of each new variation
of ultrasound machine has not been accompanied
by similar careful evaluation by controlled,
Despite decades of ultrasonic
investigation, no one can demonstrate whether
ultrasound exposure has an adverse effect at
a particular gestation, whether the effects
are cumulative or whether it is related to
the output of a particular machine or the length
of the examination. How many exposures are
too many? What is the mechanism by which growth
is affected? A large-scale study (Newnham et
al., 1991) showed decreased birthweight, although
a later study suggested the babies soon make
up the deficit. It should not be forgotten,
however, that numerous studies on rats, mice
and monkeys over the years have found reduced
fetal weight in babies that had ultrasound
in the womb compared with controls. Nor should
it be forgotten that in the monkey studies
(Tarantal et al., 1993) the ultrasound babies
sat or lay around the bottom of the cage, whereas
the little control monkeys were up to the usual
monkey tricks. Long-term follow up of the monkeys
has not been reported. Do they reproduce as
successfully as the controls? And, as Jean
Robinson has noted: "Monkeys do not learn
to read, write, multiply, sing opera, or play
the violin." Human children do, and perhaps
we should consider seriously whether the huge
increases in children with dyslexia and learning
difficulties are a direct result of ultrasound
exposure in the womb. Furthermore, when a woman
is scanned her baby’s ovaries are also
scanned. So if the woman had seven scans during
her pregnancy, when her pregnant daughter eventually
presents years later at the antenatal clinic,
her developing baby will already have had seven
scans. Do women really know what they consent
to when they rush to hospital to have their
first ultrasound scan, then trustingly agree
to further scans?
Beverley A Lawrence Beech, honourary chair
of the Association for Improvements in the
Maternity Services (AIMS), is a freelance writer
and lecturer and lives in the United Kingdom.
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