|
By Sarah Buckley
When I
was pregnant with my first baby in 1990, I decided against having a
scan. This was a rather unexpected decision, as my partner and I are
both doctors and had even done pregnancy scans ourselves—rather
ineptly, but sometimes usefully—while training in family physician (GP)
obstetrics a few years earlier.
What influenced me the most
was my feeling that I could lose something important as a mother if I
allowed someone to test my baby. I knew that if a minor or uncertain
problem showed up, which is not uncommon, I would be obliged to return
again and again and that, after a while, I might feel as if my baby
belonged to the system and not to me.
In the years since
then I have had three more unscanned babies and have read many articles
and research papers about ultrasound. Nothing I have read has made me
reconsider my decision. Although ultrasound may sometimes be useful
when specific problems are suspected, my conclusion is that it is at
best ineffective, and at worse dangerous, when used as a screening tool
for every pregnant woman and her baby.
The history of ultrasound
Ultrasound
was developed during World War II to detect enemy submarines, and was
later used in the steel industry. In July 1955, Glasgow surgeon Ian
Donald borrowed an industrial machine and, using beef-steaks for
comparison, began to experiment with the abdominal tumours that he had
removed from his patients. He discovered that different tissues gave
different patterns of sound wave ‘echo’, leading him to realise that
ultrasound offered a revolutionary way to look into the mysterious
world of the growing baby.
This new technology spread rapidly
into clinical obstetrics. Commercial machines became available in 1963
and by the late 1970s ultrasound had become a routine part of obstetric
care. Today, ultrasound is seen as safe and effective, and scanning has
become a rite of passage for pregnant women in most developed
countries. In Australia, it is estimated that 99 per cent of babies are
scanned at least once in pregnancy, usually as a routine prenatal
ultrasound (RPU) at four to five months. In the US, where this cost is
borne by the insurer or privately, around 70 percent of pregnant women
have a scan, and in European countries, it is estimated that 98 percent
of pregnant women have an ultrasound, usually once in each trimester
(third) of pregnancy.
However, there is growing concern as to
its safety and usefulness. UK consumer activist Beverley Beech has
called RPU ‘The biggest uncontrolled experiment in history’ and the
Cochrane Collaborative Database—the peak authority in evidence-based medicine—concludes:
‘…no
clear benefit in terms of a substantive outcome measure like perinatal
mortality [number of babies dying around the time of birth] can yet be
discerned to result from the routine use of ultrasound… For those
considering its introduction, the benefit of the demonstrated
advantages would need to be considered against the theoretical
possibility that the use of ultrasound during pregnancy could be
hazardous, and the need for additional resources.’
The
additional resources consumed by routine ultrasound are substantial. In
1997, for example, the Australian Federal Government paid out A$39
million to subsidise pregnancy scans; an enormous expense compared to
the A$54 million paid for all other (Australian) Medicare obstetric
costs, and this figure does not include the additional costs paid by
the woman herself. In the US, an estimated US$1.2 billion would be
spent yearly if every pregnant woman had a single routine scan.
In 1987, UK radiologist, HD Meire, who had been performing pregnancy scans for 20 years, commented:
The
casual observer might be forgiven for wondering why the medical
profession is now involved in the wholesale examination of pregnant
patients with machines emanating vastly different powers of energy,
which is not proven to be harmless, to obtain information which is not
proven to be of any clinical value by operators who are not certified
as competent to perform the operations.
The situation today is unchanged on every count.
What is ultrasound?
The
term ‘ultrasound’ refers to the ultra-high frequency sound waves used
for diagnostic scanning: these waves vibrate at 10 to 20 million cycles
per second, compared to 10 to 20 thousand cycles per second for audible
sound. Ultrasound waves are emitted by a transducer (the part of the
machine that is put onto the body), and a picture of the underlying
tissues is built up from the pattern of echo waves that return to the
transducer. Hard surfaces such as bone will return a stronger echo than
soft tissue or fluids, giving the bony skeleton a white appearance on
the screen.
Ordinary scans use pulses of ultrasound that last
only a fraction of a second, with the interval between pulses being
used by the machine to interpret the echo that returns. In contrast,
Doppler techniques, which are used in specialised scans, foetal
monitors and hand-held foetal stethoscopes (Sonicaid) use continuous
waves, giving much higher levels of exposure than pulsed ultrasound.
Many women do not realise that the small machines used to monitor their
baby’s heartbeat are actually using Doppler ultrasound, although with
fairly low exposure levels.
More recently ultrasonographers have
begun using vaginal ultrasound, where the transducer is placed high in
the pregnant woman’s vagina, much closer to her developing baby. This
is used mostly in early pregnancy, when abdominal scans can give poor
pictures. However, with vaginal ultrasound there is little intervening
tissue to shield the baby, who is at a vulnerable stage of development,
and exposure levels are high. Having a vaginal ultrasound is not a
pleasant procedure for the woman; the term ‘diagnostic rape’ was coined
to describe how some women experience this procedure.
Another
recent application for ultrasound is the nuchal (neck) translucency
(NT) test, where the thickness of the skinfold at the back of the
baby’s head is measured at around three months. A slight increase in
the thickness of the nuchal fold makes a baby more likely,
statistically, to have Down syndrome. When the baby’s risk is estimated
to be over one in 250 to 300, a definitive test is recommended. Around
19 out of 20 babies diagnosed as high risk by nuchal translucency will
not turn out to be affected by Down syndrome, and their mothers will
have experienced several weeks of unnecessary anxiety. A nuchal
translucency scan does not detect all babies affected by Down syndrome.
Information gained from ultrasound
Ultrasound
is mainly used for two purposes in pregnancy—either to investigate a
possible problem at any stage of pregnancy, or as a routine scan at
around 18 to 20 weeks.
If there is bleeding in early pregnancy,
for example, ultrasound may predict whether miscarriage is inevitable.
Later in pregnancy, ultrasound can be used when a baby is not growing,
or when a breech baby or twins are suspected. In these cases the
information gained from ultrasound can be very useful in
decision-making for the woman and her carers. However, the use of
routine prenatal ultrasound is more controversial, as this involves
scanning all pregnant women in the hope of improving the outcome for
some mothers and babies.
Routine prenatal ultrasound (RPU) also
known as a morphology scan, is designed to check the size and integrity
of the baby. The timing of routine scans (18 to 20 weeks) is chosen for
practical reasons. It offers a reasonably accurate due date—although
dating is most accurate at the early stages of pregnancy, when babies
vary the least in size—and the baby is big enough to see most of the
abnormalities that are detectable on ultrasound. However, at this
stage, the expected date of delivery (EDD) is only accurate to a week
on either side of the given date, and some studies have suggested that
an early examination, or calculations based on a woman’s menstrual
cycle, can be as accurate as RPU.
While many women are reassured
by a normal scan, RPU actually detects only between 17 per cent and 85
per cent of the one in 50 babies that have major abnormalities at
birth. A 1997 study from Brisbane, Australia, showed that ultrasound
at a major women’s hospital missed around 40 per cent of abnormalities,
with most of these being difficult or impossible to detect. Major
causes of intellectual disability such as cerebral palsy and Down
syndrome are unlikely to be picked up on a routine scan, as are heart
and kidney abnormalities.
When an abnormality is reported,
there is a small chance that the finding is a false positive, where the
ultrasound diagnosis is wrong and the baby is, in fact, healthy. A UK
survey showed that, for one in 200 babies aborted for major
abnormalities, the diagnosis on post-mortem was less severe than
predicted by ultrasound, and the termination was probably unjustified.
In this survey, 2.4 per cent of the babies diagnosed with major
malformations, but not aborted, had conditions that were significantly
over or under-diagnosed.
There are also many cases of error
with more minor abnormalities, which can cause anxiety and repeated
scans, and there are some conditions which have been seen to
spontaneously resolve.
As well as false positives, there are
also uncertain cases, where the ultrasound findings cannot be easily
interpreted, and the outcome for the baby is not known. In one study
involving women at high risk, almost 10 per cent of scans were
uncertain. This can create immense anxiety for the woman and her
family, and this worry may not be allayed by the birth of a normal
baby. In the same study, mothers with uncertain diagnoses were still
anxious three months after the birth of their baby.
These
uncertainties include the so-called ‘soft markers’; conditions that do
not cause problems, but which are sometimes linked with more serious
diagnoses such as Down syndrome. These include choroid plexus cysts in
the brain, echogenic (a brighter ultrasound image than expected) bowel
and heart areas, short femur, short humerus and pyelectasis of the
kidney (enlargement of part of the kidney). Around one per cent of
babies, for example, have a choroid plexus cyst but only one in 150 of
these babies will have a chromosomal abnormality such as Down syndrome.
Some experts have suggested that soft markers should only be disclosed
to women at high risk of abnormality.
In some cases of
uncertainty, the doubt can be resolved by further tests such as
amniocentesis. In this situation, there may be up to a two-week wait
for results, during which time a mother has to decide if she would
terminate the pregnancy if an abnormality is found. Some mothers who
ultimately receive reassuring news have felt that this process has
interfered with their relationship with their baby.
As well as
estimating the EDD and checking for major abnormalities, RPU can also
identify a low-lying placenta (placenta praevia), and detect the
presence of more than one baby at an early stage of pregnancy. However,
19 out of 20 women who have placenta praevia detected on an early scan
will be needlessly worried; the placenta will effectively move up, and
not cause problems at the birth. Furthermore, detection of placenta
praevia by RPU has not been found to be safer than detection in labour.
No improvement in outcome has been shown for multiple pregnancies
either; the vast majority of these will be detected before labour, even
without RPU.
The American College of Obstetricians and
Gynecologists, in their guidelines on routine ultrasound in low-risk
pregnancy, conclude:
‘In a population of women with low-risk
pregnancies, neither a reduction in perinatal morbidity [harm to babies
around the time of birth] and mortality nor a lower rate of unnecessary
interventions can be expected from routine diagnostic ultrasound. Thus
ultrasound should be performed for specific indications in low-risk
pregnancy.’
Biological effects of ultrasound
Ultrasound
waves are known to affect tissues in two main ways. Firstly, the sonic
beam causes heating of the highlighted area by about one degree Celsius
(1.8° F). This is presumed to be non-significant, based on whole-body
heating in pregnancy, which seems to be safe up to 2.5º Celsius (4.5º
F). Doppler scans, which use continuous waves, can cause more
significant heating, especially in the baby’s developing brain.
The
second recognised effect is cavitation, where the small pockets of gas
that exist within mammalian tissue vibrate and then collapse. In this
situation:
‘… temperatures of many thousands of degrees Celsius in
the gas create a wide range of chemical products, some of which are
potentially toxic. These violent processes may be produced by
micro-second pulses of the kind which are used in medical diagnosis…’
The
significance of cavitation effects in human tissue remains uncertain.
However, a number of studies have suggested that these effects may be
of real concern in living tissues. The first study suggesting problems
was a study on cells grown in a lab. Cell abnormalities caused by
exposure to ultrasound were seen to persist for several generations. A
more recent study involving newborn rats, who are at a similar stage of
brain development to humans at four to five months in utero, showed
that ultrasound can damage the myelin that covers nerves, indicating
that the nervous system may be particularly susceptible to damage from
this technology.
Another animal study published in 2001 showed
that exposing mice to dosages typical of obstetric ultrasound caused a
22 per cent reduction in the rate of cell division, and a doubling of
the rate of apoptosis (programmed cell death) in the cells of the small
intestine. Other researchers have found that a single ten-minute
ultrasound exposure in pregnancy affects the locomotor and learning
abilities of mice offspring in adulthood, with a greater effect from
longer exposure time.
Experts in this area have expressed
concern, especially in relation to exposure of the developing central
nervous system, whose tissues are sensitive to damage by physical
agents such as heat and ultrasound. Barnett notes that heating of the
baby’s brain is more likely after the first trimester (three months),
as the baby’s bone is more developed, and can reflect and concentrate
the ultrasound waves. Barnett warns, ‘When modern sophisticated
equipment is used at maximum operating settings for Doppler
examinations, the acoustic outputs are sufficient to produce obvious
biological effects.’
Mole comments:
‘If exposure to
ultrasound… does cause death of cells, then the practice of ultrasonic
imaging at 16 to 18 weeks will cause loss of neurones [brain cells]
with little prospect of replacement of lost cells… The vulnerability is
not for malformation but for maldevelopment leading to mental
impairment caused by overall reduction in the number of functioning
neurones in the future cerebral hemispheres.’
Recent
research has found that ultrasound also induces bleeding in the lung.
The American Institute of Ultrasound in Medicine (AIUM) recently
concluded:
‘There exists abundant peer-reviewed published
scientific research that clearly and convincingly documents that
ultrasound at commercial diagnostic levels can produce lung damage and
focal haemorrhage [bleeding] in a variety of mammalian species… The
degree to which this is a clinically significant problem in humans is
not known.’
Human studies
Studies
on humans exposed to ultrasound have shown that possible adverse
effects include premature ovulation, preterm labour or miscarriage, low
birth weight, poorer condition at birth, perinatal death, dyslexia,
delayed speech development, and less right-handedness. Non
right-handedness (left-handedness and ambidexterity) is a consistent
finding in many studies and is, in other circumstances, seen as a
marker of damage to the developing brain. One Australian study showed
that babies exposed to five or more Doppler ultrasounds were 30 per
cent more likely to develop intrauterine growth retardation (IUGR)—a
condition that ultrasound is often used to detect.
Two
long-term randomised controlled trials in Sweden and Norway compared
exposed and unexposed (or less exposed) children’s development at eight
to nine years old, and found no measurable effect on growth,
development and learning, However, as above, there was more
non-right-handedness in the offspring. It is difficult to gain
reassurance from these trials because, for example, in the Helsinki
study, 77 percent of the supposedly unexposed group actually had a
scan, and in the major branch of the Norwegian trial, scanning time was
only three minutes. And, as the authors note, intensities used today
are many times higher than in 1979–81.
A more recent randomised
trial, comparing outcomes after single and multiple pregnancy (Doppler)
scans, has produced some degree of reassurance, finding no differences
in the learning and motor functions of offspring followed to eight
years old. This study did not, however, include a group of unexposed
children, so we do not know whether these children’s outcomes are
actually normal. It is also noteworthy that almost 45 percent of the
‘single scan’ group received two or more scans. The researchers state,
‘…our results do not lessen our need to undertake further studies of
potential bio-effects of prenatal ultrasound scans.’
A recent
summary of the safety of ultrasound in human studies, published in May
2002, in the prestigious US journal, Epidemiology, suggested:
Continued
research is needed to evaluate the potential adverse effects of
ultrasound exposure during pregnancy. These studies should measure the
acoustic output, exposure time, number of exposures per subject, and
the timing during the pregnancy when exposure(s) occurred.
These
authors concluded: ‘Until long-term effects can be evaluated across
generations, caution should be exercised when using this modality
during pregnancy.’
Ultrasound exposure and dose
As
these authors imply, we need to know the exposure involved in all
studies of ultrasound, but this is not easy to measure because there is
a huge range of output, or dose, possible from a single machine.
Ultrasound machines can give comparable pictures using a lower, or a
5,000 times higher, output and, because of the complexity of machines,
it has been difficult to quantify the output for each examination.
Furthermore,
the incredibly fine details that we are now seeing on scans come at the
cost of substantial increases in output. Recent changes to US FDA
regulations now allow operators to use ultrasound machines at very high
outputs, exposing unborn babies to intensities up to eight times higher
than previously allowed, provided the output is displayed on the
machine.
This new regulation gives operators a worryingly high
degree of self-regulation, and its success in protecting unborn babies
from harm depends on an appreciation, by each operator, of complex
biophysical interactions (which are not well understood) and of the
risk-benefit involved in every examination. Such expectations may not
be realistic; in Australia, the UK, US, and most other countries,
ultrasonography training is voluntary, even for obstetricians, and the
skill and experience of operators varies widely. It also seems that few
operators are aware of research findings such as those mentioned above.
As the AIUM noted in 2000:
‘... the responsibility of an
informed decision concerning possible adverse effects of ultrasound in
comparison to desired information will probably become more important
over the next few years.’
Women’s experiences of ultrasound
Women
have not been consulted at any stage in the development of this
technology, and their experiences and wishes are presumed to coincide
with, or be less important than, the medical information that
ultrasound provides. For example, supporters of RPU presume that early
diagnosis and termination is beneficial to the affected woman and her
family. However, the discovery of a major abnormality on RPU can lead
to very difficult decision-making.
Some women who agree to have
an ultrasound are unaware that they may get information about their
baby that they do not want, as they would not contemplate a
termination. Other women can feel pressured to have a termination, or
at the least feel some emotional distancing, when their baby is
diagnosed with a possible abnormality.
Furthermore, there is
no evidence that women who have chosen termination for a baby with a
lethal abnormality are, in the long term, psychologically better off
than women whose babies have died at birth; in fact, there are
suggestions that the opposite may be true in some cases. When
termination has been chosen, women are unlikely to share their story
with others and can experience considerable guilt and pain from the
knowledge that they themselves chose the loss.
When a minor
abnormality is found —which may or may not be present at birth, as
discussed above—a woman can feel that some of the pleasure has been
taken away from her pregnancy. And the process of prenatal diagnosis
can cause harm to the baby if it generates a high degree of anxiety—and
high levels of stress hormones—in the mother, especially in the first
half of pregnancy.
Women’s experiences with ultrasound, and
other tests used for prenatal diagnosis such as amniocentesis, are
thoughtfully presented in the book The Tentative Pregnancy by Barbara
Katz Rothman. The author documents the heartache that women can go
through when a difficult diagnosis is made; for some women, this pain
can take years to resolve (These issues are further explored in
byronchild [now Kindred] Sept 04, number 11).
Ultrasound also
represents yet another way in which the deep internal knowledge that a
mother has of her body, and her baby, is made secondary to
technological information that comes from an expert using a machine;
thus the cult of the expert is imprinted from the earliest weeks of
life.
Furthermore, by treating the baby as a separate being,
ultrasound artificially splits mother from baby well before this
separation is a physiological or psychic reality. This further
emphasises our culture’s favouring of individualism over mutuality and
sets the scene for possible—but to my mind artificial—conflicts of
interest between mother and baby in pregnancy, birth and parenting.
Conclusions and recommendations
I
urge all pregnant women to think deeply before they choose to have a
routine ultrasound. It is not compulsory, despite what some may say,
and the risks, benefits, and implications of scanning need to be
considered by each mother for herself and her baby, according to their
specific situation.
If you choose to have a scan, be clear about
the information that you do and do not want to be told. Have your scan
done by an operator with a high level of skill and experience (usually
this means performing at least 750 scans per year), and say that you
want the shortest scan possible. Ask them to fill out the form (or give
you the information), and then sign it.
If an abnormality is
found, ask for counselling and a second opinion as soon as practical.
And remember that it’s your baby, your body and your choice.
Dr Sarah J Buckley
is a GP, mother of four and author of the internationally-acclaimed
book Gentle Birth, Gentle Mothering: the wisdom and science of gentle
choices in pregnancy, birth and parenting. For more information see
www.sarahjbuckley.com
First published in Nexus magazine, vol 9, no 6, October–November 2002. This version updated and published in Gentle Birth, Gentle Mothering: The wisdom and science of gentle choices in pregnancy, birth and parenting. Available from Kindred.
Published in Kindred, issue 24, December 07
See also, Be Proactive with your Prenatal Care pubished as part of the same feature in Kindred.
References
• Wagner M. Ultrasound: more harm than good? Midwifery Today Int Midwife (50):28-30.
•
de Crespigny L, Dredge R. Which Tests for my Unborn Baby?– Ultrasound
and other prenatal tests. 2nd ed. Melbourne: Oxford University Press,
1996.
• Oakley A. The history of ultrasonography in obstetrics. Birth 1986;13(1):8-13.
•
Martin J, et al. Births: Final data for 2002. National vital statistics
reports. Hyattsville MD: National Center for Health Statistics, 2003.
•
Levi S. Routine ultrasound screening of congenital anomalies. An
overview of the European experience. Ann NY Acad Sci 1998;847:86-98.
• Beech BL. Ultrasound unsound? Talk at Mercy Hospital, Melbourne, April 1993.
• Neilson JP. Ultrasound for fetal assessment in early pregnancy. Cochrane Database Syst Rev 2000(2):CD000182.
•
Senate Community Affairs Reference Group. Rocking the Cradle; A report
into childbirth procedures. Canberra: Commonwealth of Australia, 1999.
• Meire HB. The safety of diagnostic ultrasound. Br J Obstet Gynaecol 1987;94(12):11212, p 1122.
•
Kieler H, et al. Comparison of ultrasonic measurement of biparietal
diameter and last menstrual period as a predictor of day of delivery in
women with regular 28 day cycles. Acta Obstet Gynecol Scand
1993;72(5):347-9.
• Olsen O, Aaroe Clausen J. Routine ultrasound
dating has not been shown to be more accurate than the calendar method.
Br J Obstet Gynaecol 1997;104(11):1221-2.
• Shirley IM, et al.
Routine radiographer screening for fetal abnormalities by ultrasound in
an unselected low risk population. Br J Radiol 1992;65(775):564-9.
•
Luck CA. Value of routine ultrasound scanning at 19 weeks: a four year
study of 8849 deliveries. Br Med J 1992;304(6840):1474-8.
• Ewigman
BG, et al. Effect of prenatal ultrasound screening on perinatal
outcome. RADIUS Study Group. N Engl J Med 1993;329(12):821-7.
•
Chitty LS, et al. Effectiveness of routine ultrasonography in detecting
fetal structural abnormalities in a low risk population. Br Med J
1991;303(6811):1165-9.
• Chan F. Limitations of ultrasound.
Perinatal Society of Australia and New Zealand 1st Annual Congress.
Fremantle, Australia, 1997.
• Brand IR, et al. Specificity of
antenatal ultrasound in the Yorkshire Region: a Prospective study of
2261 ultrasound detected anomalies. Br J Obstet Gynaecol
1994;101(5):392-7.
• Saari-Kemppainen A, et al. Ultrasound
screening and perinatal mortality: controlled trial of systematic
one-stage screening in pregnancy. The Helsinki Ultrasound Trial. Lancet
1990;336(8712):387-91.
• Sparling JW, et al. The relationship of obstetric ultrasound to parent and infant behavior. Obstet Gynecol 1988;72(6):902-7.
• Whittle M. Ultrasonographic ‘soft markers’ of fetal chromosomal defects. Br Med J 1997;314(7085):918.
• Stewart TL. Screening for aneuploidy: the genetic sonogram. Obstet Gynecol Clin North Am 2004;31(1):21-33.
•
Brookes A. Women’s experience of routine prenatal ultrasound.
Healthsharing Women: The Newsletter of Healthsharing Women’s Health
Resource Service, Melbourne 1994/5;5(3-4):1-5.
• American College
of Obstetricians and Gynecologists. ACOG practice patterns. Routine
ultrasound in low-risk pregnancy. Number 5, August 1997. Int J Gynaecol
Obstet 1997;59(3):273-8.
• American Institute of Ultrasound in
Medicine Bioeffects Committee. Bioeffects Considerations for the safety
of diagnostic ultrasound. J Ultrasound Med 1988;7(9 Suppl):S1-38.
• Barnett SB. Intracranial temperature elevation from diagnostic ultrasound. Ultrasound Med Biol 2001;27(7):883-8.
•
Liebeskind D, et al. Diagnostic ultrasound: effects on the DNA and
growth patterns of animal cells. Radiology 1979;131(1):177-84.
• Ellisman MH, et al. Diagnostic levels of ultrasound may disrupt myelination. Exp Neurol 1987;98(1):78-92.
•
Stanton MT, et al. Diagnostic ultrasound induces change within numbers
of cryptal mitotic and apoptotic cells in small intestine. Life Sci
2001;68(13):1471-5.
• Suresh R, et al. Long-term effects of
diagnostic ultrasound during fetal period on postnatal development and
adult behavior of mouse. Life Sci 2002;71(3):339-50.
• Barnett SB,
Maulik D. Guidelines and recommendations for safe use of Doppler
ultrasound in perinatal applications. J Matern Fetal Med
2001;10(2):75-84, p 75.
• Mole R. Possible hazards of imaging and Doppler ultrasound in obstetrics. Birth1986;13 Suppl:23-33 p 26.
•
American Institute of Ultrasound in Medicine. Section 4—bioeffects in
tissues with gas bodies. American Institute of Ultrasound in Medicine.
J Ultrasound Med 2000;19(2):97-108, 154-68, p 107.
• Testart J, et al. Premature ovulation after ovarian ultrasonography. Br J Obstet Gynaecol 1982;89(9):694-700.
•
Lorenz RP, et al. Randomized prospective trial comparing
ultrasonography and pelvic examination for preterm labor surveillance.
Am J Obstet Gynecol 1990;162(6):1603 7; discussion 1607-10.
•
Geerts LT, et al. Routine obstetric ultrasound examinations in South
Africa: cost and effect on perinatal outcome—a prospective randomised
controlled trial. Br J Obstet Gynaecol 1996;103(6):501-7.
• Newnham
JP, et al. Effects of frequent ultrasound during pregnancy: a
randomised controlled trial. Lancet 1993;342(8876):887-91.
•
Newnham JP, et al. Doppler flow velocity waveform analysis in high risk
pregnancies: a randomized controlled trial. Br J Obstet Gynaecol
1991;98(10):956-63.
• Davies JA, et al. Randomised controlled trial
of Doppler ultrasound screening of placental perfusion during
pregnancy. Lancet 1992;340(8831):1299-303.
• Stark CR, et al.
Short- and long-term risks after exposure to diagnostic ultrasound in]
utero. Obstet Gynecol 1984;63(2):194-200.
• Campbell JD, et al.
Case-control study of prenatal ultrasonography exposure in children
with delayed speech. Can Med Assoc J 1993;149(10):1435-40.
• Kieler
H, et al. Routine ultrasound screening in pregnancy and the children’s
subsequent handedness. Early Hum Dev 1998;50(2):233-45.
• Kieler H,
et al. Sinistrality—a side-effect of prenatal sonography: a comparative
study of young men. Epidemiology 2001;12(6):618-23.
• Salvesen KA,
Eik-Nes SH. Ultrasound during pregnancy and subsequent childhood
non-right-handedness: a meta-analysis. Ultrasound Obstet Gynecol
1999;13(4):241-6.
• Salvesen KA, et al. Routine ultrasonography in
utero and subsequent handedness and neurological development. Br Med J
1993;307(6897):159-64.
• Odent M. Where does handedness come from?
Handedness from a primal health research perspective. Primal Health
Research 1998;6(1):1-6.
• Kieler H, et al. Routine ultrasound
screening in pregnancy and the children’s subsequent neurologic
development. Obstet Gynecol 1998;91(5 Pt 1):750-6.
• Kieler H, et
al. Routine ultrasound screening in pregnancy and the children’s
subsequent growth, vision and hearing. Br J Obstet Gynaecol
1997;104(11):1267-72.
• Salvesen KA, et al. Routine ultrasonography
in utero and subsequent growth during childhood. Ultrasound Obstet
Gynecol 1993;3(1):6-10.
• Salvesen KA, et al. Routine ultrasonography in utero and speech development. Ultrasound Obstet Gynecol 1994;4(2):101-3.
•
Salvesen KA, et al. Routine ultrasonography in utero and subsequent
vision and hearing at primary school age. Ultrasound Obstet Gynecol
1992;2(4):243-4, 245-7.
• Salvesen KA, et al. Routine ultrasonography in utero and school performance at age 8-9 years. Lancet 1992;339(8785):85-9.
•
Newnham JP, et al. Effects of repeated prenatal ultrasound examinations
on childhood outcome up to 8 years of age: follow-up of a randomised
controlled trial. Lancet 2004;364(9450):2038-44.
• Newnham JP, et
al. Effects of repeated prenatal ultrasound examinations on childhood
outcome up to 8 years of age: follow-up of a randomised controlled
trial. Lancet 2004;364(9450):2038-44, p 2043.
• Marinac-Dabic D, et
al. The safety of prenatal ultrasound exposure in human studies.
Epidemiology 2002;13(3 Suppl):S19-22., p S19.
• Marinac-Dabic D, et
al. The safety of prenatal ultrasound exposure in human studies.
Epidemiology 2002;13(3 Suppl):S19-22., p S22.
• Meire HB. The safety of diagnostic ultrasound. Br J Obstet Gynaecol 1987;94(12):1121-2.57.
• American Institute of Ultrasound in Medicine. Section 7—discussion of the mechanical index
Barnett
SB, Maulik D. Guidelines and recommendations for safe use of Doppler
ultrasound in perinatal applications. J Matern Fetal Med
2001;10(2):75-84.
• Fowlkes JB, Holland CK. Mechanical bioeffects
from diagnostic ultrasound: AIUM consensus statements. American
Institute of Ultrasound in Medicine. J Ultrasound Med 2000;19(2):69-72,
p 70.
• Watkins D. An alternative to termination of pregnancy. Practitioner 1989;233(1472):990, 992.
Loach E. The hardest thing I have ever done. (Melbourne) Sunday Herald Sun 2003 August 3 2004;8-12.
• Mulder EJ, et al. Prenatal maternal stress: effects on pregnancy and the (unborn) child. Early Hum Dev 2002;70(1-2):3-14.
• Rothman B. The Tentative Pregnancy. Amniocentesis and the sexual politics of motherhood. 2nd ed. London: Pandora, 1994.
Kindred strives to adhere to strict advertising guidelines. Please help us keep our Google Ads in alignment with Kindred's values. Contact us with the URL of any ad on this page if you think it is contradictory to our content.Thank you. |
shopping cart 
