Are Ultrasounds Safe? The Doctor Weighs In

You’re walking through the mall and your eye catches sight of a sign that reads. “Want to make your baby’s first movie? Get a fetal video today!”

Many mothers-to-be happily pay for a keepsake that is essentially a fetal ultrasound, never wondering about the ultrasound’s safety. After all, they receive ultrasounds at their obstetrician’s office, so what’s the difference? According to Dr. Carol Rumack, Professor of Radiology and Pediatrics at the University of Colorado, the difference may be much greater than you think.

What is an Ultrasound?

Believe it or not, the ultrasound did not start out as a medical tool at all. In fact, the ultrasound transducer (that wand that they pass over your stomach) was invented as a tool to locate submarines during World War II. The ultrasound would send out a sonar, or sound beam, which would bounce off a submarine and return to the source. Based on the timing of the beam’s return, the ultrasound would be able to calculate how far away the submarine was located and how big it was. Ironically, the ultrasound does the same thing with babies. The sound beam from the transducer bounces off of the baby and returns, and the computer puts together the information based on this phenomenon to figure out the shape, size, and location of the baby. In fact, today’s ultrasounds can give a relatively accurate picture of the baby’s form.

Down With Ultrasounds!

Some people actually swear off ultrasounds for all of pregnancy; others limit them to one or two per pregnancy. These people may draw a parallel between X-rays and ultrasounds. After all, for decades after the X-ray was discovered, doctors encouraged people to use X-rays for absolutely any purpose, and with virtually no precautions at all. Even when researchers finally discovered a link between cancer and X-rays, the public was stunned. How could X-rays not be safe?

Ultrasounds have not currently been linked to cancer or any other condition, but those wary of ultrasounds point out that not much research has been done on the subject. Why is this so? According to Dr. Rumack, ultrasounds are “not as risky as x-rays, so we don’t really have the manpower to go out there and investigate.” Although this has some people worried, Dr. Rumack maintains that the comparison is faulty, especially when ultrasounds are used correctly.

Possible Risks

So what are the possible risks of an ultrasound? There are two main suspects in the ultrasound controversy: heat and cavitation. Realize that fetuses can be sensitive to heat (hence the fact that pregnant women should not soak in a very hot bathtub), and that the sound energy released from the ultrasound transducer can raise the temperature of the fetus. This heat also causes cavitation, or the formation of bubbles in tissue, which some studies indicate may be detrimental to developing tissue.

Note that the only studies on the effects of heat and cavitation on human tissue have been done on a tissue culture, not on people, and that they involved very high levels of energy and a long heating period.

So should pregnant women avoid ultrasounds during pregnancy because of these risks? Dr. Rumack’s answer is adamant: they should not. “Doctors have not seen any proof regarding risks in a regular diagnostic ultrasound,” she maintains. “It’s obviously much safer than x-rays are. At the same time, it should only be given when medically needed—both because of the very small risks attached to it and because it is a waste of medical dollars when it is unnecessary.”

These risks, Rumack says, have almost nothing to do with a typical ultrasound. After all, ultrasound machines have an upper bound on the amount of energy that can be released, and this bound is set as low as reasonably possible. Experienced ultrasound techs are also trained to take certain safety precautions during the ultrasound process, such as using the ultrasound for only a limited amount of time and moving the transducer so that it does not rest for long in any one place.