How sound is ultrasound?
Ultrasound testing – a wonderful diagnostic tool and an aid to bonding with your unborn baby? Or yet another unsafe, untested piece of technology in the barrage of interventions faced by pregnant women today?
For many women ultrasound is an inevitable, even welcome, part of their regular antenatal visits – a reassuring opportunity to see the baby, and to check that all is well. For doctors, ultrasound technology offers a non-invasive way to screen for abnormalities and detect problems at an early stage. It is estimated that over one billion dollars is spent annually in the U.S. for prenatal ultrasounds1. Frequency of ultrasound tests has become a benchmark of “good prenatal care” and women who do not have access to this technology are increasingly considered deprived. In some European countries, codes of practice exist which recommend women be offered a certain number of scans – in Germany for example a minimum of two scans during pregnancy is now seen as a “right”.
Yet ultrasound screening is not without controversy. Both the safety of the ultrasound technology itself, as well as the usefulness of the information gleaned from it, continue to be the subject of heated debate. In this article we explore some of the current issues regarding the routine use of ultrasound during pregnancy and ask what you, as doulas and childbirth educators, can do to help your clients find their way through this technological maze.
Ultrasound on the increase
Evidence suggests that both the frequency with which women are being offered ultrasound testing, and the length of time their fetuses are being exposed to ultrasound, is on the increase. Especially in countries where private obstetric-led care in the norm, many women are being exposed to more and more ultrasound tests - women considered “low risk” may receive as many as eight or nine scans during a pregnancy. Higher-intensity ultrasound scans, such as 3-D or 4-D color scans, previously only offered to those women whose earlier screening had revealed a problem, are now being given on request or even offered proactively by caregivers. Women who do not have these advanced level scans routinely may begin to feel they are “missing out” on something valuable.
… there is very little evidence that the information gained from early pregnancy ultrasound screening actually improves the eventual outcome of the pregnancy.
It seems that ultrasound is popular with parents – many look forward to their routine scans, perhaps bringing relatives such as grandparents to get their first glimpse of the baby. In the United States, non-medical facilities such as Fetal Fotos of Salt Lake City, Utah, are springing up to cater to this demand by providing parents with photographs and videos of the unborn infant as souvenirs.
What is Ultrasound?
Ultrasound technology was originally developed during the 1940′s and was used in industry (to detect flaws in metal) and in warfare (to detect enemy submarines). In the 1950′s it began to be applied in medical diagnostics as a tool to detect abdominal tumors, and later, as a means of detecting gross fetal abnormalities such as anencephaly. Since then, the technology has become more refined and is able to detect ever more subtle indications of fetal well-being.
The term “ultrasound” refers to the very high frequency sound waves produced by ultrasound transmitters or transducers. When these sound waves hit a dense mass, such as bone or tissue, they produce echoes, which bounce back to a receiver. This receiver then translates these echoes into a signal that can be converted into either sound (fetal heartbeat) or an image.
Ultrasound technology is used in a number of pieces of equipment – not only the familiar “scan” used in pregnancy, but also in Doptone equipment (used to detect the fetal heartbeat), and electronic fetal monitoring equipment used during labor. A fairly recent innovation is the development of the vaginal probe used very early in pregnancy when the uterus is too low in the abdomen for a regular scan to be effective.
Why is Ultrasound used?
Ultrasound technology has many possible applications, including:
- Confirming pregnancy and checking for multiple pregnancies
- Estimating gestational age
- Checking fetal growth
- Checking indications of fetal well-being including blood flow to and from the placenta, and the amount of amniotic fluid present
- Investigating problems such as suspected spontaneous abortion (miscarriage), bleeding during pregnancy, or abnormalities of the placenta
- Screening for abnormalities such as spina bifida
- Confirming the position of the baby and assisting in procedures, which require the position of the baby to be known e.g. amniocentesis and external cephalic version
Is Ultrasound useful?
In evaluating the usefulness of ultrasound, there are two key issues. Firstly, how reliable is ultrasound as a means on diagnosing abnormalities, and secondly, what can be done with that data once it has been obtained?
Available evidence indicates that routine ultrasound testing during early pregnancy does have some benefits – improved estimation of gestational age, earlier detection of multiple pregnancy, and earlier detection of some forms of fetal abnormality. There is evidence to suggest that for many women, confirmation of fetal life at an early stage in pregnancy is reassuring and improves their confidence in the pregnancy.
Despite this, there is very little evidence that the information gained from early pregnancy ultrasound screening actually improves the eventual outcome of the pregnancy. For example, in the case of a suspected miscarriage, ultrasound can be used to quickly to detect whether or not the fetal heart is beating. While that information may be eagerly sought by a woman who believes she is about to miscarry, there is little evidence to suggest that having that information is clinically useful or will improve the outcome for the fetus one way or the other. The scan though cannot determine the risk of the baby dying at a later stage of pregnancy.
Screening for fetal abnormality is equally problematic. Screening for abnormalities such as spina bifida (neural tube defects) is most accurate when carried out between 11-14 weeks of pregnancy2. However, this is simply a screening tool and cannot be used to diagnose the condition. The scan can have false positive results, which means that many women would go on to have further and more invasive testing such as amniocentesis to confirm the diagnosis. In the worst case scenario she might opt for an early termination, when in fact the pregnancy is normal. One UK study suggested that as many as 1 in 200 pregnancies terminated for major abnormalities could have been wrongly diagnosed3. At the same time, there are many abnormalities that cannot be reliably detected on a scan – for example, cerebral palsy.
To know definitively whether or not the baby has a neural tube defect the mother can choose to have amniocentesis. This is not usually done until 15-18 weeks of pregnancy. By the time the mother receives the results she is often in her 20th week and is then faced with the decision to terminate a pregnancy with an induction of labor if the test shows her baby to have spina bifida. While chorionic villus sampling (CVS) can be carried out earlier, it is not possible to diagnose spina bifida from this test. In addition, there are risks with amniocentesis. The test has an accuracy rate of 95% – amongst women with normal amniocentesis results, 2 out of 100 babies are still born with fetal abnormalities. There is also a risk of miscarriage (1 in 200-400 pregnancies) and uterine infection (1 in 1,000 pregnancies)4. The other concern with having ultrasound scans to detect abnormalities is that whilst the scan may identify a possible problem there is no way of determining the severity. Conditions such as spina bifida can result in varying degrees of disability5. Some children with this abnormality have complete paralysis whilst others may have limited mobility. Hydrocephalus is commonly found with spina bifida but can often be corrected by the use of a shunt at birth. Mental disability can occur, but many children with spina bifida have no mental disability, are well integrated into normal schools and have a high degree of independence.
Scans done in the first or second trimester are often used to estimate gestational birth weight and estimated due date. However, this in itself can be problematic. A scan carried out at 20 weeks to determine estimated due date, for example, has an error margin of +/- 11 days. When comparing the accuracy of ultrasound scanning with the mother’s estimate of what her baby would weigh, the scan was not any more accurate6. Scanning may also be used to determine fetal growth and the presence of fetal growth retardation. In this case the scan has an error margin of 10%. Since clinical decisions such as whether or not to induce a labor may be dependant on these results the implications of an inaccurate assessment is clearly important. Randomized controlled trials suggest that ultrasound scanning in late pregnancy is associated with a much higher level of intervention, including early admission to hospital, with no detectable improvement in fetal outcome3.
There is no doubt that in certain circumstances ultrasound technology can be an immensely useful tool. However, there remains a question as to whether ultrasound should be routinely offered to all women or only used in specific circumstances.
Is Ultrasound safe?
Nobody really knows and everyone has a different view. There has been surprisingly little research to identify whether or not ultrasound has any negative effect on fetal health or subsequent health in childhood or adult life.
A number of studies have suggested that ultrasound waves can have a damaging effect on living tissue. Studies on animals have demonstrated a number of such effects including nerve damage, and an increase in the rate of cell death.
In humans, studies have suggested a wide variety of possible problems related to exposure to ultrasound including premature ovulation, premature labor, and low birth weight7. Other studies have suggested long term effects include a possible relationship with childhood cancers especially leukemia, as well as delayed speech development and dyslexia. There is some evidence that as few as two ultrasounds could affect brain development. Research carried out in Sweden found a higher incidence of left-handedness in men who had been given two scans when they were fetuses. While being left handed is not a health concern, it does raise the question whether or not the ultrasound itself affects the structure and organization of the brain.
Unfortunately many of these trials have been too small or flawed in their methodology. None of the randomized controlled trials have been large enough to yield any firm data one way or the other. The fact is we simply do not know. One of the main problems for researchers is that ultrasound technology has not been around long enough for long term data to be collated. Record keeping is also a problematic area with no common standards for recording when and for how long women have been exposed to ultrasound in pregnancy.
In addition there are no international standards on how a scan should be carried out. Each caregiver has their own policies and practices in relation to the frequency with which they recommend scanning, variable time of exposure and different types and age of equipment affecting accuracy and level of exposure.
Helping clients make an informed choice
As with any intervention, ultrasound has both advantages and risks, which may not be easy to quantify. Each couple will have their own perspective on the potential benefits of having an ultrasound (peace of mind, early detection of abnormality, and so on) versus the potential risks (potential for harm to the unborn baby, danger of “false positive” or unclear results).
By the time you meet your clients they may be some way into their pregnancy and therefore already have had several ultrasounds – indeed they may not even see ultrasound screening as a choice to be made, since it has become such a common part of prenatal care.
You can talk to your clients about the benefits and disadvantages of ultrasound scans, helping them to explore why they are choosing to have the tests and what information are they looking for. Encourage them to ask their caregivers about the tests, the purpose and what will the results be used for. Working through potential scenarios of what they will do if the scan reveals a problem can be beneficial. Most people expect the scan to tell them that they are having a healthy baby and are reluctant to consider the possibilities of an abnormality. Discussing this though assists them in determining how they would feel about further testing and the potential consequences of a scan. You can also discuss the alternatives to ultrasound – other indicators such as abdominal palpation and fundal height measurements may meet their need of knowing the baby is growing well for example.
Ultrasound on the web
There are many excellent sources of information about ultrasound screening in pregnancy available on the web.
Contains links to a number of recent news articles about ultrasound
A history of the development of ultrasound technology
MIDIRs informed choice series of leaflets for professionals includes one on ultrasound screening in pregnancy. You can receive the full set of leaflets sent to you via email in PDF format for a very low cost. There is also a set of the same titles available for parents.
- Wagner, M. 1999. Ultrasound: More Harm than Good? Midwifery Today, 50.
- Nicolaides, K.H., Sebire, N.J., & Snijders, R.J.M. The 11-14 week scan: Nuchal translucency thickness. The Fetal Medicine Centre. Retrieved September 21st 2003, from http://www.fetalmedicine.com/11
- Buckley, S. 2002. Ultrasound Scans: Cause for Concern. Nexus Magazine 9 (6).
- University of Pennysylvania Health System. (2001). Amniocentesis. Retrieved September 22nd 2003, from http://www.pennhealth.com/health_info/pregnancy/
- Foster, M.R. 2003. Spina Bifida. E-Medicine. Retirieved September 22nd 2003, from http://www.emedicine.com/orthoped/topic557.htm
- Baum, J.D., Gussman. D., & Wirth, J.C. III. 2002. Clinical and Patient Estimation of Fetal Weight vs. Ultrasound Estimation. Journal of Reproductive Medicine, 47(3),194-198.
- Enkin, M. Keirse, M.J.N.C., Neilson, J., Crowther, C., Duley, L., Hodnett, E., et.al. (2000). A guide to effective care in pregnancy and childbirth (3rd ed.). Oxford: Oxford University Press.
How does Childbirth International training address this?
All Childbirth International courses focus on evidence-based care and explore the evidence for common medical interventions.
All courses are provided through flexible learning, meaning you can study at home, in your own time. No need for workshops, travel or child care. When choosing a training program, consider whether you want to get through your training as quickly as possible in order to be certified, or if you want the most comprehensive training that will help you develop both professionally and personally.
Childbirth International is a truly diverse international training organization. With students in 75 countries, from every corner of the globe, we celebrate the differences, similarities and uniqueness of each culture, religion and race. Providing the most comprehensive and flexible training available for birth professionals you can truly make a difference within your community.
Childbirth International offers training programs for Birth Doulas, Postpartum Doulas, Childbirth Educators and Breastfeeding Counselors. We also have an advanced training course available for birth professionals to help you build and grow your business.