Written by Dana
What Are the Risks of Ultrasound?
The intention of this article is not to cause fear or guilt. As I mentioned in Part I, there is no absolute proof that ultrasound in pregnancy harms the baby. However, there is enough evidence to warrant concern and more careful consideration than often occurs. The article is intended to educate about the implications of prenatal ultrasound exams so that women and their partners can make more fully informed decisions.
Biological Risks
There are two recognized biological effects of ultrasound:
Overheating- When ultrasound waves are focused on living tissue, the temperature in that area rises. The temperature increase depends on the type of tissue, but seems to be about 1 degree Celsius. This is assumed to be safe since neurological damage to the fetus seems to occur only beyond a 2.5 degree temperature increase in the mother’s whole body. The concern though, is that the unborn child might be significantly affected by a lower, but more localized temperature increase caused by focused ultrasound waves. Also, a 1999 study suggests that heating in third-trimester fetal tissues during prenatal ultrasound may be as high as 5.8*C.[1]
Cavitation- Ultrasound waves can cause pockets of gas inside tissues to vibrate and collapse. It is thought that human tissues may be susceptible to cavitation, and that its effects may include release of toxins or bleeding in small blood vessels.[2]
Other Possible Biological Effects
Sarah Buckley touches on a number of other possible biological effects of ultrasound in the Ultrasound Scans chapter of her book “Gentle Birth, Gentle Mothering”. These include increased free radical formation and possible changes in “important cell properties such as permeability…. adverse effects not only on embryogenesis (early development), but also on late prenatal and postnatal development” caused by acoustic streaming.
Also included are effects indicated by animal studies, such as
- cell abnormalities
- myelin damage
- reduction in cell division rate
- increase in apoptosis (programmed cell death)
- brain hemorrhages
- locomotor and learning disabilities
- neuronal cell migration abnormalities
- lower birth weight
- lower white blood cell counts
Some human studies were also covered in “Gentle Birth, Gentle Mothering”. These single or small studies showed possible effects which include
premature ovulation, preterm labor or miscarriage, low birth weight, poorer condition at birth, perinatal death, dyslexia, delayed speech development, and less righthandedness. Nonright-handedness (left-handedness or ambidexterity) is a consistent finding in many ultrasound studies, including the more authoritative randomized controlled trials, and is, in some circumstances, a marker of damage or disruption to the developing brain.
Other Considerations
Noise Level for Baby- Mayo Clinic’s Dr. Mostafa Fatemi’s research[3] led him to conclude that “ultrasound vibrations sound like the high tones of a piano, at about the same volume as an approaching subway train.”[4]
Stress- Many women look forward to their ultrasound for reassurance that everything is okay with the baby. But what if the ultrasound indicates an abnormality? Further testing may be required to confirm a finding. And what if nothing can be done about it anyway? Some families welcome the opportunity to have time to come to terms with the information. Others would find the rest of the pregnancy very stressful. The March of Dimes says that “very high levels of stress may contribute to preterm birth or low birthweight in full-term babies.”[5]
False positives and false negatives- Ultrasound exams may reveal an abnormality when there isn’t one (or when it resolves prior to the end of the pregnancy). They may also find nothing when there actually is a problem. While ultrasound provides a remarkable window into the womb, it is not a perfect diagnostic tool.
Pressure to Abort-Following an unfavorable finding, some women are faced with pressure to terminate the pregnancy.
Increasingly Common Birth Defects- In her Midwifery Today article [6], Caroline Rodgers wonders whether there might be a connection between the increase in unexplained birth defects and use of prenatal ultrasound. She specifically mentions genital and urinary tract birth defects (“among the most common birth defects….specific causes of most of these conditions are unknown”[7], according to the March of Dimes) and heart defects. Both areas of the body can undergo particular scrutiny during an ultrasound exam.
Less Use and Undervaluing of Clinical Examination- As ultrasound use becomes routine, clinical examination skills may be used less and expertise may drop. These hands-on skills are critical because they are cost effective and can be done on the spot without specialized equipment. Also there is great value in the human connection afforded by clinical examinations such as palpation (examination by touching), and unfortunately that connection can be impaired by reliance on technology.
Part III: Benefits of Ultrasound
1.Whittingham, T.A. (Jul 2001). Estimated Fetal Cerebral Ultrasound Exposures From Clinical Examinations. Ultrasound in Medicine & Biology, Volume 27, Issue 7, Pages 877-882. Retrieved June 28, 2010 from http://www.ncbi.nlm.nih.gov/pubmed/11476918.
2.Buckley, Sarah J. (2009). Gentle Birth, Gentle Mothering, Berkeley, CA: Celestial Arts.
3. Fatemi, M. & Ogburn P.L. Jr & Greenleaf, J.F. (Aug 2001). Fetal Stimulation by Pulsed Diagnostic Ultrasound. In the Journal of Ultrasound in Medicine, Vol 20, Issue 8, Pages 883-889. Retrieved June 28, 2010 from http://www.ncbi.nlm.nih.gov/pubmed/11503925?dopt=Abstract.
5. The Osgood File. (Jan 2003). Ultra Hearing Fetus. CBS Radio Network. Retrieved May 30, 2010 from http://www.acfnewsource.org/science/ultra_hearing_fetus.html.
5. March of Dimes. Pregnancy and Newborn: Heath Education Center. Retrieved June 28, 2010 from http://www.marchofdimes.com/pnhec/159_527.asp.
6. Rodgers, Caroline. (Winter 2006). Questions About Prenatal Ultrasound and the Alarming Increase in Autism. In Midwifery Today, Issue 80. Retrieved June 29, 2010 from http://www.midwiferytoday.com/articles/ultrasoundrodgers.asp.
7. March of Dimes. Professionals and Researchers: Genital and Urinary Tract Defects. Retrieved June 29, 2010 from http://www.marchofdimes.com/professionals/14332_1215.asp.
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