Ultrasound is like ordinary sound except it has a frequency (or pitch) higher than people can hear. Ultrasound is sent into the body from a scanning instrument (transducer) placed on a patient's skin. The sound is reflected off structures inside the body and is analyzed by a computer to make a picture of these structures on a monitor similar to a television screen. The moving pictures can be recorded on film or videotape. Diagnostic ultrasound is also called "sonography."

In most clinical settings, a diagnostic medical sonographer -- an allied health professional who has been trained specifically to perform ultrasound examinations -- will perform the examination. Following the completion of the examination, the sonographer will review the images and the patient's history with a doctor trained in the interpretation of ultrasound. Although a sonographer or a technologist may play a critical role in extracting the information essential to deriving a diagnosis, the rendering of a final diagnosis of ultrasound studies represents the practice of medicine, and, therefore, is the responsibility of the supervising doctor

There are no known harmful effects associated with the diagnostic use of ultrasound. Widespread clinical use of diagnostic ultrasound for many years has not revealed any harmful effects. Although the possibility exists that such biological effects may be identified in the future, current data indicate that the benefits to patients of the prudent use of diagnostic ultrasound outweigh the risks, if any, that may be present. However, a prudent and conservative approach is recommended in which diagnostic ultrasound is to be used only for medical benefit and with minimal exposure.

Ultrasound is a safe and non-invasive diagnostic tool that can be used to examine many parts of the body, most commonly soft tissue. It is used extensively in the female pelvis (both obstetrical and gynecological), the abdomen (kidneys, liver and gallbladder), and for cardiac diagnosis. Another type of ultrasound, Doppler, is used in vascular diagnosis to assess blood flow. Other areas, such as the brain, eyes, thyroid, breast, prostate, and testicles, can be imaged by ultrasound as well. (It's also frequently used during your prenatal appointments to hear your baby's heartbeat.)

Ultrasound is widely known for its use in first-, second-, and third-trimester pregnancy. The most common reason for having an ultrasound examination during pregnancy is to help the doctor determine when your baby is due, or to make sure the baby is growing as it should. A doctor may also request an ultrasound examination to determine the baby's position, to see if you are carrying twins or triplets, or to detect a birth defect.

Ultrasound should be used in a prudent manner, only to provide medical benefit to the patient. The AIUM strongly discourages the nonmedical use of ultrasound for psychosocial or entertainment purposes. The use of ultrasound to only view the fetus, obtain a picture of the fetus, or determine the fetal gender without a medical indication is inappropriate and contrary to responsible medical practice

The female reproductory organs are positioned in the body in such a way that when the bladder is full, ultrasound waves get conducted through the water filled bladder and provide a clear imaging of the organs. In the absence of the water in the bladder, ultrasound waves get diffused and imaging becomes difficult. Hence patients are asked to come with a “full bladder”.

The doctor has to take images at several critical positions of the fetus to take measurements so that she can assess the well being of the fetus. A fetus is in its own world in the mother’s womb and many times it does not keep still to enable such measurements. Taking critical sections, therefore consumes a lot of time of the doctor. In some extreme cases, appointments might be rescheduled because the fetus might never present itself in the right position to be scanned. This behavior of the fetus is beyond the control of the doctor and this invariably results in delays.