|
Lapochka
Немного написал(а)
Зарегистрирован:Декабрь 2010
Сообщений: 48
Географическое положение: Москва
Пол: Женский
|
Натали
Re: УЗИ при беременности
Для думающих:
Ultrasound Scans- Cause for Concern
@ Dr Sarah J. Buckley MD 2005 www.sarahbuckley.com
Previously versions have been published in Mothering magazine, issue 102, Sept-Oct 2000, and Nexus magazine, vol 9, no 6, Oct-Nov 2002.
A fully updated and expanded version is published in Gentle Birth, Gentle Mothering: A Doctor's Guide to Natural Childbirth and Gentle Early Parenting Choices (Sarah J Buckley MD, Celestial Arts, 2009).
Look out for the new Prenatal Ultrasound ebook-audio package coming soon!
See other ebook-audio packages
When I was pregnant with my first baby in 1990, I decided against having a scan. This was a rather unusual decision, as my partner and I are both doctors and had even done pregnancy scans ourselves- rather ineptly, but sometimes usefully- while training in GP/family physician obstetrics a few years earlier.
What influenced me the most was my feeling that I would 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 and this is not uncommon -- that I would be obliged to return again and again, and that after a while, it would 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.
Ultrasound Past and Present
Ultrasound was developed during WWII to detect enemy submarines, and was subsequently used in the steel industry. In July 1955 Glasgow surgeon Ian Donald borrowed an industrial machine and, using beefsteaks as controls, began to experiment with abdominal tumours that he had removed from his patients. He discovered that different tissues gave different patterns of ultrasound "echo", leading him to realise that ultrasound offered a revolutionary way to look into the previously mysterious world of the growing baby.1
This new technology spread rapidly into clinical obstetrics. Commercial machines became available in 19632 and by the late 1970's ultrasound had become a routine part of obstetric care.3 Today, ultrasound is seen as safe and effective and scanning has become a rite of passage for pregnant women in developed countries. Here in Australia, it is estimated that 99 percent of babies are scanned at least once in pregnancy mostly as a routine prenatal ultrasound (RPU) at 4 to 5 months. In the US, where this cost is borne by the insurer or privately, around 70 percent of pregnant women have a scan.4
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",5 and the Cochrane Collaborative Database the peak scientific authority in medicine-concludes that,
...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.6
This seems a very poor reward for the huge costs involved. In 1997-8, for example, $39 million was paid by the Australian federal government for pregnancy scans- an enormous expense compared to $54 million for all other obstetric medicare costs.7 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 H.D.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.8
The situation today is unchanged, on every count.
The 1999 Senate Committee report, 'Rocking the Cradle' recommended that the cost-benefit of routine scanning, and of current ultrasound practices, be formally assessed. Recommendations were also made to develop guidelines for the safe use of all obstetric ultrasound, as well as for the development of standards for the training of ultrasonographers (see below). So far, none of these recommendations have been implemented.7
What is Ultrasound?
The term "ultrasound" refers to the ultra-high frequency soundwaves used for diagnostic scanning. These waves travel at 10 to 20 million cycles per second, compared to10 to 20 thousand cycles per second for audible sound.2 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 which return. 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 waves being used by the machine to interpret the echo that returns. In contrast, Doppler techniques, which are used in specialised scans, fetal monitors and hand-held fetal stethoscopes ("sonicaids") feature continuous waves, giving much higher levels of exposure than 'pulsed' ultrasound. Many women do not realise that the small machines used to listen to their baby's heartbeat are actually using Doppler ultrasound, although with fairly low exposure levels.
More recently, ultrasonographers have been using vaginal ultrasound, where the transducer is placed high in the vagina, much closer to the 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 will be 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 vaginal scans.
Another recent application for ultrasound is the "nuchal translucency test", where the thickness of the skin fold at the back of the baby's head is measured at around 3 months; a thick 'nuchal (neck) fold' makes the baby more likely, statistically, to have Downs syndrome.
When the baby's risk is estimated to be over one in 250, a definitive test is recommended. This involves taking some of the baby's tissue by amniocentesis or chorionic villus sampling. Around 19 out of 20 babies diagnosed as 'high risk' by nuchal translucency will not turn out to be affected by Down's syndrome, and their mothers will have experienced several weeks of unnecessary anxiety.
A nuchal translucency scan does not detect all babies affected by Down's syndrome. (For more about prenatal testing, see Sarah's article, on prenatal diagnosis, coming soon as ebook and audio package.)
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 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 may be very useful in decision-making for the woman and her carers. However the use of routine prenatal ultrasound (RPU) is more controversial, as this involves scanning all pregnant women in the hope of improving the outcome for some mothers and babies.
The timing of routine scans (18 to 20 weeks) is chosen for pragmatic 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 EDD (expected date of delivery) is only accurate to a week either side, and some studies have suggested that an early examination, or calculations based on a woman's menstrual cycle, can be as accurate as RPU.9 10
And while many women are reassured by a normal scan, RPU actually detects only between 17 and 85 percent of the 1 in 50 babies that have major abnormalities at birth.11 12 A recent study from Brisbane showed that ultrasound at a major women's hospital missed around 40 percent of abnormalities, with most of these being difficult or impossible to detect.13 Major causes of intellectual disability such as cerebral palsy and Down's syndrome are unlikely to be picked up on a routine scan, as are heart and kidney abnormalities.
When an abnormality is detected, there is a small chance that the finding is a "false positive", where the ultrasound diagnosis is wrong. 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 percent of the babies diagnosed with major malformations, but not aborted, had conditions that were significantly over or under-diagnosed.14
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.15
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 percent of scans were uncertain.16 This can create immense anxiety for the woman and her family, and the worry may not be allayed by the birth of a normal baby. In the same study, mothers with "questionable" diagnoses still had this anxiety three months after the birth of their baby.
In some cases of uncertainty, the doubt can be resolved by further tests such as amniocentesis. In this situation, there may be up to two weeks wait for results, during which time a mother has to decide if she would terminate the pregnancy if an abnormality is found. Even mothers who receive reassuring news have felt that this process has interfered with their relationship with their baby.17
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.15 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, in their 1997 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.18
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 one 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.19
The second recognised effect is cavitation, where the small pockets of gas which 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....19
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.20 Another study showed that, in newborn rats, (who are at a similar stage of brain development to humans at four to five months in utero), ultrasound can damage the myelin that covers nerves,21 indicating that the nervous system may be particularly susceptible to damage from this technology.
Brennan and colleagues, reported 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.22
Mole 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.23
Studies on humans exposed to ultrasound have shown that possible adverse effects include premature ovulation,24 preterm labour or miscarriage,15 25 low birth weight,26 27 poorer condition at birth,28 29 perinatal death,28-30 dyslexia,31 delayed speech development,32 and less right-handedness.33-36 Non right-handedness is, in other circumstances, seen as a marker of damage to the developing brain.35 37 One Australian study showed that babies exposed to 5 or more doppler ultrasounds were 30% more likely to develop intrauterine growth retardation (IUGR)- a condition that ultrasound is often used to detect.26
Two long-term randomised controlled trials, comparing exposed and unexposed childrens' development at eight ti nine years old, found no measurable effect from ultrasound.38 39 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.40 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 huge range of output, or dose, possible from a single machine. Modern machines can give comparable ultrasound pictures using a lower, or a 5 000 times higher dose,8 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.41 In Australia training is voluntary, even for obstetricians, and the skill and experience of operators varies widely.
A summary of the safety of ultrasound in human studies, published in May 2002 in the prestigious US journal 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.42
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/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.17 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.43 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.
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.
Women's experiences with ultrasound and other tests used for prenatal diagnosis (eg amniocentesis) are thoughtfully presented in the book The Tentative Pregnancy by Barbara Katz Rothman.44 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. She suggests that the large numbers of screening tests currently being offered to check for abnormalities may make every woman feel that her pregnancy is 'tentative' until she receives reassuring results.
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 emphasises our cultures 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 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 to 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.
References
1. Wagner M. Ultrasound: more harm than good? Midwifery Today Int Midwife 1999(50):28-30.
2. de Crespigny L, Dredge R. Which Tests for my Unborn Baby?- Ultrasound and other prenatal tests. 2nd ed. Melbourne: Oxford University Press, 1996.
3. Oakley A. The history of ultrasonography in obstetrics. Birth 1986;13(1):8-13.
4. Martin J, et al. Births: Final data for 2002. National vital statistics reports. Hyattsville MD: National Center for Health Statistics, 2003.
5. Beech BL. Ultrasound unsound? Talk at Mercy Hospital, Melbourne, April 1993.
6. Neilson JP. Ultrasound for fetal assessment in early pregnancy. Cochrane Database Syst Rev 2000(2):CD000182.
7. Senate Community Affairs Reference Group. Rocking the Cradle; A report into childbirth procedures. Canberra: Commonwealth of Australia, 1999.
8. Meire HB. The safety of diagnostic ultrasound. Br J Obstet Gynaecol 1987;94(12):1121-2.
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.
10. 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.
11. Ewigman BG, et al. Effect of prenatal ultrasound screening on perinatal outcome. RADIUS Study Group. N Engl J Med 1993;329(12):821-7.
12. 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.
13. Chan F. Limitations of Ultrasound. Perinatal Society of Australia and New Zealand 1st Annual Congress. Freemantle, Australia, 1997.
14. Brand IR, et al. Specificity of antenatal ultrasound in the Yorkshire Region: a prospective study of 2261 ultrasound detected anomalies ACOG Committee Opinion. Number 297, August 2004. Nonmedical use of obstetric ultrasonography. Br J Obstet Gynaecol 1994;101(5):392-7.
15. 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.
16. Sparling JW, et al. The relationship of obstetric ultrasound to parent and infant behavior. Obstet Gynecol 1988;72(6):902-7.
17. 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.
18. 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.
19. 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.
20. Liebeskind D, et al. Diagnostic ultrasound: effects on the DNA and growth patterns of animal cells. Radiology 1979;131(1):177-84.
21. Ellisman MH, et al. Diagnostic levels of ultrasound may disrupt myelination. Exp Neurol 1987;98(1):78-92.
22. 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.
23. Mole R. Possible hazards of imaging and Doppler ultrasound in obstetrics. Birth 1986;13 Suppl:23-33 suppl, p 26.
24. Testart J, et al. Premature ovulation after ovarian ultrasonography. Br J Obstet Gynaecol 1982;89(9):694-700.
25. 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.
26. Newnham JP, et al. Effects of frequent ultrasound during pregnancy: a randomised controlled trial. Lancet 1993;342(8876):887-91.
27. Geerts LT, et al. Routine obstetric ultrasound examinations in South Africa: cost and effect on perinatal outcomea prospective randomised controlled trial. Br J Obstet Gynaecol 1996;103(6):501-7.
28. 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.
29. Thacker SB. Quality of controlled clinical trials. The case of imaging ultrasound in obstetrics: a review. Br J Obstet Gynaecol 1985;92(5):437-44.
30. Davies JA, et al. Randomised controlled trial of Doppler ultrasound screening of placental perfusion during pregnancy. Lancet 1992;340(8831):1299-303.
31. Stark CR, et al. Short- and long-term risks after exposure to diagnostic ultrasound in utero. Obstet Gynecol 1984;63(2):194-200.
32. 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.
33. Salvesen KA, et al. Routine ultrasonography in utero and subsequent handedness and neurological development. Br Med J 1993;307(6897):159-64.
34. 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.
35. Kieler H, et al. Sinistralitya side-effect of prenatal sonography: a comparative study of young men. Epidemiology 2001;12(6):618-23.
36. Kieler H, et al. Routine ultrasound screening in pregnancy and the children's subsequent handedness. Early Hum Dev 1998;50(2):233-45.
37. Odent M. Where does handedness come from? Handedness from a primal health research perspective. Primal Health Research 1998;6(1):1-6.
38. 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.
39. Salvesen KA, et al. Routine ultrasonography in utero and school performance at age 8-9 years. Lancet 1992;339(8785):85-9.
40. Salvesen KA, et al. Routine ultrasonography in utero and subsequent growth during childhood. Ultrasound Obstet Gynecol 1993;3(1):6-10.
41. Taylor KJ. A prudent approach to ultrasound imaging of the fetus and newborn. Birth 1990;17(4):218-21, 223; discussion 221-2.
42. Marinac-Dabic D, et al. The safety of prenatal ultrasound exposure in human studies. Epidemiology 2002;13(3 Suppl):S19-22.
43. Watkins D. An alternative to termination of pregnancy. Practitioner 1989;233(1472):990, 992.
44. Rothman B. The Tentative Pregnancy. Amniocentesis and the sexual politics of motherhood. 2nd ed. London: Pandora, 1994.
|
Я что-то подобное тоже слышала про УЗИ. Только это из разряда "маталл золото сатаны" и "женщина сасуд греха". Ерунда одним словом.
