Women believe that they can ensure the well being of their babies by having ultrasound scans and that the earlier any problems are detected, the better. But, increasing evidence now shows that early scans don't necessarily save lives and that, far from being a precise early warning system, the technology itself may be harmful.
Women who have previously miscarried or have conceived after infertility treatment often undergo additional ultrasound for reassurance. In fact, it appears that ultrasound itself may possibly increase her risks of miscarriage, or premature labour or birth.
Obstetricians in Michigan (Am J Obstet Gynecol, 1990; 162: 1603-10) studied 57 women at risk of giving birth prematurely. Half were given a weekly ultrasound examination; the rest simply had pelvic examinations. Preterm labour in the ultrasound group was more than twice that of the control group (52 per cent compared with 25 per cent).
In a larger, randomised, controlled trial from Helsinki of more than 9000 women (Lancet, 1990; 336: 387-91), 20 miscarriages occurred after 16-20 weeks in the screened group compared with none in the controls.
A later study in London (Lancet, 1992; 340: 1299-303) found four times the number of perinatal deaths of healthy infants among women having Doppler ultrasound examination of the umbilical and uterine arteries at 19-22 weeks and at 32 weeks compared with controls (16 versus 4).
Even women who use ultrasound occupationally are at risk of miscarriage. A study in Helsinki (J Epidemiol Commun Health, 1990; 44: 196-201) found that, if the physiotherapist was pregnant, handling ultrasound equipment for at least 20 hours a week significantly increased her risk of
spontaneous abortion. The risk after 10 weeks was significantly increased among women administering ultrasound for more than 10 hours a week.
A study in Oslo looked at how many of the babies born with serious defects had been diagnosed by antenatal scans and whether early diagnosis (at 17-21 weeks) made any difference to the outcomes (Acta Obstet Gynecol Scand, 1998, 177: 635-42). For those babies who had a problem, early diagnosis had no benefits: more of them died, and they were delivered sooner when they were smaller. For six babies with abdominal wall defects detected on scanning, they were operated on sooner, but the short term outcomes were the same as those who weren't scanned and operated on later. The scanned babies also stayed in hospital longer and spent more time in ventilators. The survival rate in the diagnosed group was 77 per cent versus 96 per cent in those not detected until after birth.
Of 36 babies with a variety of defects, only 36 per cent were picked up by scans.
One of the promises of antenatal scanning is that obstetricians will be able to identify the baby with growth problems and do something to help it while in the womb. However, a German study (Acta Obstet Gynecol Scand, 1998; 77: 643-89) found that, of 2378 pregnancies, only 58 out of 183 growth retarded babies were diagnosed before birth, and 45 fetuses were wrongly diagnosed as growth retarded when they were not. Only 28 of the 72 severely growth retarded babies were detected before birth despite the mothers having an average of 4.7 scans. The main difference was in invasive procedures. Preterm elective caesarean delivery was five times more frequent in those where growth retardation was diagnosed before birth. The admission rate into intensive care was three times higher for diagnosed babies.
There is a presumption of safety with ultrasound technology (just as in the days when pregnant women were told that x-rays were safe) and concerns raised in published studies have been widely ignored. In 1984, American obstetricians discovered that children between 7-12 years of age exposed to ultrasound in the womb were more likely to have dyslexia and to have been admitted to hospital during their childhood than a control group who'd never been scanned (Obstet Gynecol, 1984; 63: 194-200).
In 1993, a study in Calgary, Alberta, examined the antenatal records of 72 children with delayed speech of unknown cause and found that these children were twice as likely as controls to have been exposed to ultrasound in the womb (Can Med Assoc J, 1993; 149: 1435-40).
A Norwegian study (Lancet, 1992; 339: 85-9) showed an increase in left handedness among children exposed to ultrasound in the womb, suggesting that ultrasound may affect brain development.
Although animal studies are not necessarily applicable to humans, striking behavioural differences were noticed in baby monkeys that had been scanned (Teratology, 1993; 47: 159-70). Those exposed to ultrasound were much more passive than normal and were seen sitting or lying around on the bottom of the cage.
It is vital that we investigate whether the vast increase in the incidence of dyslexia, learning difficulties and behavioural problems seen in our children today is related to ultrasound exposure in the womb.
When a woman is scanned, her baby's ovaries and lifetime supply of eggs are also scanned. If a woman has seven scans during her pregnancy, when her daughter gets pregnant, her developing baby will already have had seven scans even before the daughter has four or five scans of her own.
It's important for us to stop presuming, as we used to do with x-rays, that endless exposure isn't harmful.