An ultrasound scan uses high frequency wave sounds to create an image of an organ in the body. Ultrasound is very high frequency sound that cannot be heard by the human ear, but can be detected using a machine called an ultrasound scanner.
It can be used to look at all soft tissue structures and blood vessels. It cannot be used to look at bones or the lungs or gastro-intestinal tract in detail.
An ultrasound scan does not use x-rays. The ultrasound waves are delivered by a small handheld sensor, which is similar to a microphone. As sound waves are used, rather than radiation, the procedure is thought to be completely safe.
As well as being used to monitor an unborn baby in a pregnant woman, ultrasound is also used to highlight congenital heart disease, examine the prostate gland, uterus and ovaries and other organs of the body. Ultrasound is also used during surgery such as biopsies (where the tissue sample is taken for analysis).