HOW DOES IT WORK?

There are various types of ultrasound that can record information in different ways. The method used depends on the circumstances. They all work on the same basic principle. Sound waves, produced by a small crystal, are directed into a specific area of the body through a microphone- like device called a transducer. The transducer is moved on the skin surface, "scanning" the area.

Another type of transducer, used in vaginal ultrasound, is designed to be inserted into the vagina to aid the doctor in examining the pelvic organ. The sound waves bounds off the tissues inside the like echoes, and are converted into an image on television-like screen.

The type of ultrasound is most often used, called real time, combines still pictures in rapid succession to show movement, similar to the frames that make the motion picture. Real time ultrasound can show the fetal heartbeats, movement of the arm, legs, and other type of the body movements. The creations of these pictures by ultrasound can show the growing fetus, the number of fetuses in the uterus, in the uterus and the position of the fetus and placenta.

Another form of the ultrasound, called Doppler ultrasound, gives audible signals. When the sound waves are reflected, they are converted into electrical signals of the fetal heartbeat. These signal are amplified so they heard by the mother and the doctor.