Ultrasound: Weighing the Propaganda
Against the Facts
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:
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 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
Babies with serious defects
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
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
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
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" (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 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 ultrasound.
Assessing the risks
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, large-scale trials.
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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