---

---

From the crude type of ultrasound available in the 1950's, ultrasound (US) has developed into a highly sophisticated diagnostic tool for use during pregnancy. Ultrasound use has grown rapidly to the point where most pregnant women now receive one or more ultrasound exams during their pregnancies. According to 1987 update report on ultrasound by Health and Welfare Canada, up to 80 percent of all newborns are exposed to ultrasound.

However, the long-term safety of such exposure for newborns has not yet been proven, and the use of ultrasound for every pregnancy is not officially recommended by experts. Both doctors and women need to take a serious look at whether such widespread use of ultrasound is really beneficial for the baby or the mother.

What Is Ultrasound ?

Ultrasound is the name given to sound waves that are much higher in pitch and frequency than can be heard by the human ear. Early in this century, scientists discovered that these high pitched sound waves travelled thorough water, and like audible sound waves, could bounce off objects in their path and return to the sender in the form of an echo. These echoes could then be collected and used to form an electronic picture of objects in the path of these waves. Along with advances in electronics, these discoveries led to the development of ultrasound as a diagnostic tool in many fields of medicine. In fact, one of the main advantages of ultrasound is that it provides information that previously could only be obtained through X-rays or even surgery.

In obstetrics, ultrasound, also called sonography, is the use of an echo sounder to produce a picture of the baby in utero. High frequency low energy sound waves are used to scan the mother's abdomen and reflect the fetus outline on an electronic screen in a series of bright dots.

In order to prepare for an obstetrical ultrasound, a woman must drink approximately six glasses of water about one hour before the exam and not empty her bladder until after the test. A full bladder is necessary to allow a better view of the uterus and the baby.

There is another type of ultrasound used during pregnancy and that is the hand held electronic stethoscope, called the Doppler Stethoscope. It is used in the office to listen to the baby's heartbeat early on in pregnancy. This could be usually done just as well using an ordinary fetal stethoscope.

The routine ultrasound exam uses pulsed ultrasound waves at a higher output, for very short periods of time. By contrast, the doppler stethoscope uses continuous low output ultrasound waves for a longer time. The overall ultrasound exposure to the fetus is greater, and it is often repeated at every prenatal visit, starting early on in the pregnancy.

The Debate On Routine Versus Selective Use Of Ultrasound

It is important to be clear on the difference between routine ultrasound and selective ultrasound.

ROUTINE ultrasound is done for healthy low risk pregnant women whose pregnancy is progressing normally. The exam is usually performed quickly and therefore may be less accurate.

SELECTIVE ULTRASOUND is done for women who are at high risk for complications during their pregnancy or who develop complications during their pregnancy. This ultrasound exam takes longer and may focus on answering specific questions posed by your doctor.