[ Continued from Page 1 ]
Biological Effects of Ultrasound
Ultrasound waves are known to affect tissues in two main ways. Firstly, the sonar beam causes heating of the highlighted area by about 1 degree Celsius. This is presumed to be non-significant based on whole-body heating in pregnancy, which seems to be safe up to 2.5 degrees Celsius (Am Inst of Ultrasound Medicine Bioeffects Report 1988).
The second recognized 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 that are used in medical diagnosis" (Am Inst of Ultrasound Medicine Bioeffects Report 1988). The significance of cavitation effects in human tissue is unknown.
A number of studies have suggested that these effects are of real concern in living tissues. The first study suggesting problems was a study on cells grown in the lab. Cell abnormalities caused by exposure to ultrasound were seen to persist for several generations (Liebeskind 1979). Another study showed that in newborn rats, who are at a similar stage of brain development to humans at 4 to 5 months in utero, ultrasound can damage the myelin that covers nerves (Ellisman 1987), indicating that the nervous system may be particularly susceptible to damage from this technology.
A 1999 animal study by Brennan and colleagues, reported in New Scientist (June 12, 1999), showed that exposing mice to dosages typical of obstetric ultrasound caused a 22 percent reduction in the rate of cell division, and a doubling of the rate of aptosis, or programmed cell death, in the cells of the small intestine.
Mole (1986) comments "If exposure to ultrasound ... causes 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 functionning neurones in the future cerebral hemispheres."
Studies on humans exposed to ultrasound have shown that possible adverse effects include:
Non right-handedness is, in other circumstances, seen as a marker of damage to the developing brain (see Odent 1998, Keiler 2001). One Australian study showed that babies exposed to 5 or more doppler ultrasounds were 30 percent more likely to develop intrauterine growth retardation (IUGR), a condition that ultrasound is often used to detect (Newnham, 1993).
Two long-term randomized controlled trials comparing exposed and unexposed children’s development at 8 to 9 years of age found no measurable effect from ultrasound (Salvesen 1992, Kieler 1998b). However, as the authors note, intensities used today are many times higher than in 1979 to 1981. Further, in the major branch of one trial scanning time was only three minutes (Salvensen 1993). More studies are obviously needed in this area, particularly in the areas of Doppler and vaginal ultrasound, where exposure levels are much higher.
A further problem with studying ultrasound’s effect is the enormous range of output, or dose, possible from a single machine. Modern machines can give comparable ultrasound pictures using a lower or a 5000 times higher dose (Meire 1987), and there are no standards to ensure that the lowest dose is used. Because of the complexity of machines, it is difficult to even quantify the dose given in each examination (Taylor 1990). In Australia training is voluntary even for obstetricians, and the skill and experience of operators varies widely.
A recent summary of the safety of ultrasound in human studies, published in May 2002 in the U.S. Journal of Epidemiology, concluded, " ... there may be a relation between prenatal ultrasound exposure and adverse outcome. Some of the reported effects include growth restriction, delayed speech, dyslexia, and non-right-handedness associated with ultrasound exposure. 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" (Marinac-Dabic 2002).
The UK consumer organization AIMS has produced a booklet, "Ultrasound Unsound?" originally published in 1993 and recently updated. This very comprehensive publication, which I highly recommend, includes a form that pregnant women undergoing ultrasound can ask their caregivers to fill out. You can make your own form based on the information below or obtain the booklet from www.birthinternational.com.au.
My Baby’s Ultrasound Exposure Record
Signature (doctor or midwife) ... ... ... ... ... ... ... ... ... ... Date ... ... ... ... ..
The ultrasonographer is asked to specify:
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/or 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 from their "abnormal" baby (Brookes, 1995).
Furthermore, there is no evidence that women who have chosen termination 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 (Watkins 1989). And 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 (MIDIRS 1996).
When minor abnormalities are found, which may or may not be present at birth as discussed above, women can feel that some of the pleasure has been taken away from their pregnancy.
To my mind, 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 is a physiological or psychic reality. This further emphasizes our cultures favoring 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 would urge all pregnant women to think deeply before they choose to have a routine ultrasound. It is not compulsory, despite what some doctors have said, and the risks, benefits and implications of scanning need to be considered for each mother and 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 as above, and sign it.
If an abnormality is found, ask for counseling and a second opinion as soon as it’s practical, and remember that it's your baby, your body and your choice.
First published in Nexus magazine, vol9, no 6, Oct-Nov 2002 and then at Red Flags Weekly February 3, 2003
This is not a new issue as I have posted articles on this over the last four years (see below), but it is one that deserves attention and consideration for those who are pregnant and considering this diagnostic procedure.
Related Articles:
Ultrasound Scans Linked to Brain Damage in Babies Ultrasound Scans May Harm Unborn Babies
Ultrasound Scans Linked to Brain Damage in Babies
Ultrasound Scans May Harm Unborn Babies
Return to Table of Contents #404