Want to reach midwives?
Advertise in Midwifery Today
for more information.
Promote your birth-related product or service.
Advertise with Midwifery Today.Click here
to check out all the options.
Through networking and education, Midwifery Today's mission is to return midwifery care to its rightful position in the family, to make midwifery care the norm throughout the world, and to redefine midwifery as a vital partnership with women.
Ultrasound: Weighing the Propaganda Against the Facts
by Beverley Lawrence Beech
© 1999 Midwifery Today, Inc. All rights reserved.
[Editor's note: This article first appeared in Midwifery Today Issue 51, Autumn 1999.]
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
In response to womens 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 group52 percentcompared
with 25 percent in the controls. Although the numbers were small the difference
was unlikely to have emerged by chance.
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
Since the publication of Ultrasound? Unsound further studies have raised questions about the value of routine ultrasound scanning.
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
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 wifes 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 sons 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. Id look for possible
behavioural changes, in reflexes, IQ, attention span" (Bolsen, 1982).
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 were found.
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 ultrasoundlower than exposures from
many machines nowadaysthe women had only two exposures, and it was
real time, not Doppler, a more powerful form of ultrasound.
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"
Donalds 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 babys
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.
- Beech, B. & Robinson, J. (1996). Ultrasound? Unsound. London: Association for Improvements in the Maternity Services (AIMS).
- Bolsen, B. (1982). Question of risk still hovers over routine prenatal use of
ultrasound. JAMA, 247: 2195-2197.
- Donald, I. (1979). Practical
Obstetric Problems. (5th ed). London: Lloyd-Luke, Medical Books Ltd.
- Donald, I. (1980). Sonar—Its present status in medicine. In A. Jurjak (Ed),
Progress in Medical Ultrasound, 1: 001–04. Amsterdam: Excerpta Medica.
- Jahn, A. et al. (1998). Routine screening for intrauterine growth retardation
in Germany; low sensitivity and questionable benefit for diagnosed cases. Acta Ob
Gyn Scand, 77: 643–89.
- Lorenz, R.P. et al. (1990, June). Randomised prospective trial comparing ultrasonography
and pelvic examination for preterm labor surveillance. Am. J. Obstet. Gynecol, 1603–10.
- Mason, G. and Baillie, C. (1997). Counselling should be provided before parents
are told of the presence of ultrasonographic soft markers of fetal abnormality
(Letter). BMJ 315: 180–81.
- Newnham, J.P. et al. (1991). Effects of frequent ultrasound during pregnancy:
a randomised controlled trial. The Lancet, 342: 887–90.
- Saari-Kemppainen et al. (1990). Ultrasound screening and perinatal mortality:
controlled trial of systematic one-stage screening in pregnancy. The Lancet, 336:
- Salvesen, K.A. et al. (1992). Routine ultrasonography in utero and school performance
at age 8–9 years. The Lancet, 339.
- Skari, H. et al. (1998). Consequences of prenatal ultrasound diagnosis: a preliminary
report on neonates with congenital malformations. Acta. Ob Gyn Scand, 177: 635–42.
- Tarantal, A.F. et al. (1993). Evaluation of the bioeffects of prenatal ultrasound
exposure in the Cynomolgus Macaque (Macaca fascicularis). Chapter III in Developmental
and Mematologic Studies, Teratology 47: 159–70.
- Taskinen, H. et al. (1990). Effects of ultrasound, shortwaves, and physical exertion
on pregnancy outcome in physiotherapists. Journal of Epidemiology and Community
Health 44: 196–201.
- Understanding Obstetric Ultrasound (2nd edition) by Jean Proud
- Midwifery Today Issue 51
Theme: Fathers in Pregnancy and Birth; articles on ultrasound, natural family planning, the "call" to midwifery, placenta previa and much more round out the issue.
- Midwifery Today Issue 50
Theme: Homebirth; from this issue, read online Ultrasound: More Harm Than Good? by Marsden Wagner
If you enjoyed this article, you'll enjoy Midwifery Today magazine! Subscribe now!