Will repeated ultrasound examinations harm my baby?
This is a question readers often ask. It's a timely question, as millions of obstetrical diagnostic exams are done every year in North America. As well, many expectant families want to record the historic moment of delivery by obtaining a high-resolution 3-D video of it. How safe are these procedures?
Research on the effects of ultrasound examinations on the fetus is inconclusive.
Ultrasonography was invented during the Second World War to prevent German submarines from sinking Allied ships. Later, Dr. Ian Donald, a Scottish doctor, used the technique to diagnose abdominal tumours. Its use quickly spread to pregnancy.
Ultrasound uses high-frequency sound waves that create images on a screen. This can be extremely useful in helping doctors to determine the cause of bleeding in early pregnancy, or in detecting twins, or abnormal positions of the fetus. No one questions its use for diagnostic purposes.
Ultrasound waves affect living tissue in two ways. The sonar beam heats the examined area to about 1 degree Celsius (2 degrees Fahrenheit). This temperature increase is believed to be safe. The second effect is known as cavitation, in which small pockets of gas within tissues vibrate, intense heat is generated and the cavity collapses. The significance of this process in human tissue is unknown. However, studies on cells grown in laboratories showed that abnormalities caused by exposure to ultrasound persisted for several generations.
Newborn rats that are at the same stage of development as humans at four to five months have been subjected to ultrasound. One study showed it can damage the myelin sheath that covers nerves, possibly indicating the nervous system may be susceptible to damage by this technique.
Another study on animals, reported in New Scientist, showed that exposing mice to dosages typical of obstetrical ultrasound caused a 22 per cent reduction in the rate of cell division and a doubling of cell death in cells of the small bowel.
But does this apply to humans? Some researchers relate miscarriage, low birth weight, dyslexia, delayed speech development and less right-handedness to obstetrical ultrasound. They question whether this is the result of damage to the developing brain.
An Australian study revealed that babies exposed to five or more ultrasounds were 30 per cent more likely to develop intrauterine growth retardation. However, two long-term studies comparing exposed and unexposed children eight to nine years old showed no measurable effect from obstetrical ultrasound. But these studies were done many years ago and scanning time was only three minutes. Today, Doppler ultrasound exposure levels are higher, and with the use of vaginal ultrasound, there is less tissue shielding the baby from the ultrasound probe.
The other concern is the wide range of doses possible from a single machine. Years ago, I discovered that X-ray machines were sometimes delivering 90 times the normal dose of radiation needed, often reaching near lethal limits. Studies show there can be a wide range of doses a fetus receives from ultrasound equipment, depending on the age of the equipment and the skill of the technician.
What concerns me is the use of 3-D high-intensity ultrasound strictly for entertainment purposes by private clinics. It's money-making marketing ploy. The enticement is that families can see, for 30 minutes or longer, a video of little Johnny or Mary bobbing around in amniotic fluid. Such clinics also stress that 3-D videos create bonding with the baby. This is absolute nonsense. A similar marketing ploy brought fathers into delivery rooms to cement family bonding. As yet, I haven't heard of any decrease in the divorce rate because of it.
To be sure, no one has proven beyond a shadow of a doubt that long exposure to 3-D ultrasound is harmful. But hell would freeze over before I would allow any of my children to be exposed to the potentially damaging effects of ultrasound vibration and heat for amusement.
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