(Excerpt from Natural Pregnancy by Lauren Feder, MD)
Ultrasound in pregnancy works by emitting ultra-high frequency sound waves, beyond the range of human hearing, which create an image of the fetus in the womb. From a transducer (or a probe) placed within the vagina in early pregnancy or on the surface of the abdomen thereafter, sound waves are emitted at millions of cycles per second. (Modern ultrasound energy intensities are higher now than in earlier decades.) Ultrasounds are used at various stages of pregnancy to assess both mother and baby.
Benefits of Ultrasound
Ultrasound uses are twofold. Prenatal ultrasound is commonly used routinely, such as in confirming pregnancy early on or inspecting fetal organs and development at approximately 18 to 20 weeks. Ultrasounds are also used to gain information on specific conditions such as bleeding, growth concerns, or the baby’s position in late pregnancy. In addition, many expectant parents look forward with great anticipation to "see” their baby on ultrasound.
In general, ultrasounds are performed for the following reasons:
• Assess uterus, ovaries, placenta
• Confirm pregnancy
• Detect multiple births
• Calculate due date
• Inspect fetal organs for growth and development
• Check gender
• Verify fetal position and breech presentation
• Inspect the placenta and placement
• Evaluate levels of amniotic fluids
• Identify pelvic abnormalities of the mother
• “See” the baby
Risks of Ultrasound
As sound waves are used instead of radiation, doctors consider ultrasound to be safe and noninvasive. For this reason, risks are often not discussed, nor considered. However, according to the American Pregnancy Association, “The long term effects of repeated ultrasound exposures on the fetus are not fully known. It is recommended that ultrasound only be used if medically indicated.” A study with 15,000 low-risk pregnancies concluded the use of routine ultrasound is debatable and does not improve outcome and therefore should be done selectively. These warnings are clearly not heeded, as it is estimated that most women in the United States will have a routine ultrasound sometime during pregnancy, and often multiple times. Moreover, ultrasound is becoming more commonplace, as women in 2006 were twice as likely to have an ultrasound in pregnancy compared to 1995. In addition, commercial ultrasound services have surfaced as a place where expectant families can make appointments for various packages from heartbeat check and gender peeks, to deluxe packages with 30-minute 3D and 4D sessions.
One of the risks of having an ultrasound, is receiving information about the results of the scan, without knowing how to decipher them. Routine ultrasound is not able to detect all abnormalities, and there can be errors in predicting a baby’s gender. According to Dr. Sarah Buckley, one study showed that routine ultrasound detects between 17 percent and 80 percent of major abnormalities, and another study from Brisbane missed approximately 40 percent of them. In addition, women have been given information about abnormalities, when in fact the baby was fine; these are known as “false positive” findings. In some cases, false positive findings have resulted in the abortion of normal babies. Needless to say, receiving an abnormal result is a great source of anxiety and stress for parents, another example of the nocebo effect.
The Heating Effects of Ultrasound
Studies have shown that women exposed to heat, such as from hot tubs or saunas, in early pregnancy have a greater risk of birth defects. However, it is recognized that ultrasound also can cause heating. During ultrasound, some of the waves are reflected while others are absorbed. The reflected waves generate the image, but the absorbed waves generate heat, causing thermal changes in the tissue and resulting in gas bubbles. This can lead to small local gas pockets in affected tissues which collapse, leaving cavities, known as cavitation. According to the National Council on Radiation Protection and Measurements (NCRPM), some machines cause temperatures to rise if the probe is left in one spot, rather than continuously moved, which may prevent harmful elevations in temperature. Theoretically, high temperature from ultrasound use can lead to production of reactive chemicals such as free radicals, which could potentially cause genetic and cell damage. The committee recommends that ultrasound technicians be aware of these risks and avoid leaving a probe in one focal area for a prolonged period of time (more than 10 minutes).
Determining the exact risks of ultrasound is complicated by the fact that ethically, scientific research and experiments cannot be conducted on pregnant women. According to researchers from Yale University, exposure to ultrasound waves disrupts brain development in fetal mice. Although the ultrasound wave levels used in the experiment were beyond those used by obstetricians, the authors said it should raise concerns about use of commercial “keepsake” ultrasound services. Although there is no evidence that it could affect brain development in human babies, “the findings indicate a need for further study and caution with nonmedical exposure.”
While doctors receive a plethora of data from scans, the expectant parents are given results which can be confusing and anxiety provoking. Most physicians assume that detection of severe fetal abnormalities will be cause for termination. Because this is rarely discussed ahead of time, many couples remain uninformed about and unprepared to deal with the implications of ultrasound findings. For example a relatively common finding in the 2nd trimester ultrasound scan is enlargement in part of the kidney (known as fetal pyelactasis), found more commonly in males and also considered a soft sign for chromosomal abnormalities.
Although the vast majority (96%) of cases are benign and resolve spontaneously in the first year of life, findings like these are an enormous cause of stress and anxiety for the family, and for no reason. For women who would not consider a termination, the information from a routine ultrasound is unnecessary. According to Beverley Beech, the chairman of the Association for Improvements in Maternity Services, "I am not sure at all that the benefits of ultrasound scans outweigh the downsides. We should be advising women to think very, very carefully before they have scans at all.” Most expectant couples are excited to be able to “see” their baby, not realizing that one of the purposes of the scan is to look for abnormalities. After receiving this information, “Women can feel pressured to have a termination, or at the least feel some emotional distancing from their “abnormal” baby,”writes Dr. Sarah Buckley. Research about ultrasound has been inconclusive, but has also suggested the following adverse effects:
• Increased left-handedness in children (according to researchers, exposure to ultrasound in utero increases the risk of left-handedness in males, which suggests that ultrasound affects the fetal brain)
• Cell abnormalities
• Damage to myelin sheath covering the nerves
• Early labor
• Low birth weight
• Restricted fetal growth
• Premature birth
• Poorer health in newborns, and perinatal death
• Increased learning disabilities
• Delayed speech
It is presumed that use of ultrasound and the information it provides is considered valuable and essential for every pregnancy. As with many of the tests and procedures performed during pregnancy, it is important to consider the risks, benefits, and implications of the test. Ultrasound is an elective test, it is not mandatory. During my pregnancies, I declined all ultrasound and Doppler tests, deferring instead to the archaic obstetric stethoscope which meant my midwife could hear my baby’s heartbeat by my 20th week, late compared to ultrasound standards!
Even my parents tried to convince me to have an ultrasound, as they considered their grandchild-to-be worthy of state-of-the-art ultrasound technology. As I told them, I made my decision based on several factors. Many people were given too much medical information that did not necessarily improve pregnancy outcome and only caused anguish for the family. I chose to trust my body’s internal wisdom, rather than rely on a routine ultrasound. My colleagues reassured me that ultrasound was harmless. However, I knew there had been many instances in the past decades in which pregnant women were reassured by their doctors that use of x-ray, DES (diethylstilbestrol), and thalidomide were harmless, only to learn after the fact, that there were side effects. (The medication DES is a synthetic estrogen that was prescribed from 1938 to 1971 for pregnant women who had experienced miscarriages and premature deliveries. Although it was considered safe, it was found to be linked to health risks in both sons and daughters including risk of vaginal cancer (in offspring), breast cancer, pregnancy complications, and infertility. The German drug, Thalidomide, prescribed in the late 1950s for anxiety, insomnia, and morning sickness in pregnant women, was found to cause malformation of limbs and other birth defects.) In addition, I knew that I would not consider termination, so I felt the information was unwarranted. Being somewhat old-fashioned, I looked forward to finding out whether my baby was a boy or girl, at birth! And in the end, I just wanted to enjoy my pregnancies.
But let’s be realistic. Living in our modern world, most pregnant women will undergo a minimum number of ultrasounds. If you are having an ultrasound, consider the following:
• Use ultrasound sparingly and avoid unnecessary scans
• Work with an experienced ultrasonography technician at a reputable site
• Use a scan machine that provides the least exposure in the shortest amount of time.
References: See Dr. Lauren's Natural Pregnancy book.