And it is true that the very short pulses of sound that produce echoes and ultimately the pictures you see on the screen when they hit soft tissue – 1,000 pulses to a second, each lasting one-millionth of a second – have never been definitely shown to cause heating or bubbles in the tissues of human babies.6
Nevertheless, this position ignores a growing body of medical evidence to the contrary, so much so that all of the pertinent US regulatory bodies urge obstetricians not to use ultrasound routinely.
The enthusiastic and uncritical embracing of this new technology reminds many of what happened in the US with diethylstilbestrol (DES), the wonder drug of the fifties that was supposed to cure miscarriage. The side-effects of the drug are only now showing up in adult offspring some 30 years later, in the form of reproductive problems and cancer.
The fact is, any woman who has had a foetal ultrasound scan is participating in one of the biggest laboratory experiments in medical history. Both in the US and the UK, the regulatory bodies approved the use of ultrasound without any long-term studies being done, leading the public to assume that the procedures are safe.
‘No well controlled study has yet proved that routine scanning of prenatal patients will improve the outcome of pregnancy.’ That was the official statement put forward by the American College of Obstetrics and Gynecology (ACOG) in 1984.7 At a 1988 meeting in London jointly held by the Royal Society of Medicine and the ACOG, several top obstetricians, as well as the executive director of the ACOG, disclosed that of eight major studies attempting to evaluate the effectiveness of ultrasound, ‘none has shown [that] routine use improves either maternal or infant outcome over that achieved when diagnostic ultrasound was used only when medically indicated.’8
As studies into the effects of ultrasound began to be done in the late eighties and nineties, they confirmed these early suspicions. Two researchers in Switzerland did an analysis of all the scientific (that is, randomized, controlled) studies of ultrasound scanning to evaluate its effect on the outcome of pregnancy. Their conclusion: ultrasound doesn’t make one bit of difference to the ultimate health of the baby. This means it doesn’t improve the live birth rate or help to produce fewer problem babies.9 One reason it makes no difference in terms of live births is that the babies who are usually aborted after a scan shows up a severe malformation are usually those who would have died during pregnancy or shortly after birth, anyway.
The only good reason to use ultrasound, the researchers concluded, is to screen for gross congenital malformations – not to ensure your baby is ‘all right’, the usual vague rationale offered to most pregnant woman with no suspicious symptoms.
Another study of 15,000 American women also found ‘no significant differences in the rate of adverse perinatal outcome (foetal or neonatal death or substantial neonatal morbidity)’ between those scanned and those in the control group. The number of premature babies were identical in the two groups, as were the outcomes of multiple births, late-term pregnancies and small-for-dates babies.10 As Dr Richard Berkowitz of New York’s Mount Sinai Medical Center concluded: ‘None of the studies published to date demonstrates an effect on the outcome of pregnancy in most low-risk women.’11
In fact, some studies show that, with ultrasound, you are more likely to lose your baby. A study from Queen Charlotte’s and Chelsea Hospital in London found that women having doppler ultrasound were more likely to lose their babies than those who received only standard neonatal care (17 deaths to 7).12 It can increase the risk of miscarriage,13 even among women exposed to occupational sonography for more than 10 hours a week.14
It has been shown to trigger premature birth, doubling the rate in at-risk women given weekly scans.15 The evidence is fairly conclusive that ultrasound doesn’t do any good in normal pregnancies. But does subjecting an embryo to ultrasound at a delicate stage of development do any lasting harm? New studies have emerged showing that ultrasound scanning may indeed cause subtle brain damage. According to a Norwegian study of 2,000 babies, performed by the National Centre for Foetal Medicine in Trondheim, those subjected to routine ultrasound scanning were 30 per cent more likely to be left-handed than those who weren’t scanned.16 This predilection for left-handedness appears to show up only in boys. In a later analysis of 177,000 Swedish men, those whose mothers had scans were 32 per cent more likely to be left-handed.17 In Britain, the rate of left-handedness has more than doubled – from 5 per cent in the 1920s to 11 per cent today. Neurologists believe that slight brain damage can cause right-handed people to become left-handed.
Evidence from Australia demonstrates that frequent scans also appear to restrict growth.18 Exposure to ultrasound also causes delayed speech, according to Canadian research. Professor James Campbell, an ear, nose and throat surgeon in Alberta, Canada, compared a group of 72 children who had speech problems with a similar group with no such difficulties. He found that most of those with delayed speech had been exposed to ultrasound in the womb, whereas most of those with normal speech had not. ‘The possibility of subtle microscopic changes in developing neural tissue exposed to ultrasound waves has to be considered,’ he concluded.19
These findings are particularly alarming given that the women in the study had only one scan apiece. Most pregnancies in Britain and North America involve at least two scans, and others many more, whether or not there is even a whiff of a problem.
Animals have exhibited delayed neuromuscular development, altered emotional behaviour and lowered birthweight with exposure at the equivalent of current diagnostic levels.20 Rodents exposed to high-intensity ultrasound have also had low birthweights and nerve damage.21
Children who’d been exposed to ultrasound in the womb had a higher incidence of dyslexia, according to one study.22 Mothers whose babies were scanned show a 90 per cent increase in foetal activity,23 the effect of which on their future development is anyone’s guess. Ultrasound also exposes the foetus to a loud noise of 100 decibels, similar to the highest notes on a piano – as loud as an underground train arriving at a station.24
Work performed in the laboratory may provide some clues as to how scanning could cause damage. We know that sonography produces biological effects in two ways: heat and cavitation (the production of bubbles which expand and contract with the sound waves). We also know that ultrasound causes shock waves in liquid, but we don’t know if it does so in human tissue – or for that matter, amniotic fluid. Finally, we don’t know whether the effects are cumulative – that is, if they increase with multiple exposure or duration. This is an important issue now that doctors routinely order multiple scans. It also may have a bearing on electronic foetal monitoring, which employs ultrasound (although at one-thousandth of a scan’s peak intensity) to monitor the baby’s heartbeat during labour and delivery, often by being aimed at one spot for 24 hours.
