Dangers of a Fetal Doppler


A fetal doppler, or doppler stethoscope, has become the accepted method for fetal heart tone monitoring in the United States. Used regularly by obstetricians, and available for over-the-counter purchase by patients, dopplers are not risk free.

With a lack of long-term or large studies conducted on fetal dopplers, these devices are avoided by some midwives and pregnant women.

What is a Doppler?

A fetal doppler is a type of ultrasound that uses doptones to hear a fetus's heartrate. The echoes of the heartbeat are translated into a "swish/thump" noise that physicians interpret. The frequency concentration level of a fetal doppler is greater than that of a general ultrasound machine, due to the need to penetrate deeper into the body and detect the heart tone. In fact, according to Anne Frye, midwife and author of "Understanding Lab Work in the Childbearing Year," one minute of doppler exposure equals 35 minutes of real-time ultrasound.


Ultrasound was originally developed to detect enemy submarines during WWII. In 1955, surgeon Ian Donald discovered that the machines could be used to see through certain tissues, each of which gave off a different "wave." By the 1970s, ultrasound had become a routine procedure for pregnant women.


As with any medical test, there are some advantages to having a doppler or times when it is necessary. For example, dopplers can be used to hear fetal heart tone at week 10 of a pregnancy, much earlier than a stethoscope. By hearing the tone at this earlier time, miscarriages can be detected and appropriately dealt with before surgery is required. Stronger doptone devices are used to detect heart murmurs and heart defects in foetuses to allow physicians time to prepare for emergency surgeries that may be required at birth.


Some studies have found side effects of ultrasound use on foetuses. The primary risk theory encompasses a theoretical concept known as cavitation. According to Dr. Sears, paediatrician and author of "The Birth Book," "When sound waves bombard laboratory tissues at high frequencies, they shake up the molecules, heat them, and produce microscopic gas bubbles in the cell called 'cavitation.' Whether this heat or these bubbles damage the cell is unknown, although studies suggest that the changes demonstrated in research test tubes are insignificant in babies." While this concern is theoretical in nature, it has prompted many organisations, including the National Institutes of Health Task Force on Diagnostic Ultrasound, to advise physicians against any form of routine ultrasound. In fact, the FDA in an article cautioning parents against over-the-counter use of doppler stethoscopes states, "The number of sessions or the length of a session to which a foetus is exposed is uncontrolled, thus raising the potential for harm to the foetus."

Other tests have revealed possible links between ultrasound use and growth retardation, left-handedness, dyslexia and delayed speech development. A study by Dr. Newnham and published in the British Journal of Obstetrics and Gynecology found that babies exposed to five or more doppler ultrasounds were 30 per cent more likely to develop intrauterine growth retardation--a condition ultrasound is often used to detect.


As with any medical procedure, parents should weigh the risks and rewards. Ultrasound technology is a growing business in the medical practice, and as such is consistently offered and advertised as safe. As with many medical technologies, ultrasound has been given the label of being safe until proved dangerous and limited studies have been done to effectively prove or disprove the theories. If desiring an alternative to a doppler, ask the health care provider to use a fetoscope. Fetoscopes are expertly used by midwives for regular appointments with much success, producing the same result without any risk to the developing foetus.