What Is Ultrasound?
Ultrasound is energy in the form of sound waves produced by a small crystal. The sound waves move at a frequency too high to be heard by the human ear. They are directed into a specific area of the body through a device called a transducer. The type of ultrasound that is most often used, called real-time, combines still pictures one after another to show movement, somewhat like the single frames that make a motion picture.

Ways Ultrasound Is Used
Ultrasound is often used to help find a possible problem or check a known condition. It is an important diagnostic tool that gives information other tests do not.

Obstetrics
Ultrasound is used in obstetrics to examine the growing fetus inside the mother's uterus.

Ultrasound can provide valuable information about the fetus's health and well-being, including:

• Age of the fetus
• Rate of growth of the fetus
• Placement of the placenta
• Fetal position, movement, breathing and heart rate
• Amount of amniotic fluid in the uterus
• Number of fetuses
• Some birth defects

Gynecology
Ultrasound is used in gynecology to examine the pelvic organs and — along with Mammographyn — the breasts. Ultrasound can help:

• Identify a pelvic or breast mass
• Show the location and characteristics of a mass
• Detect problems causing pelvic pain
• Locate the position of an intrauterine device (IUD)
• Monitor ovulation in treating infertility

The Exam
Ultrasound exams are done in doctors' offices or hospitals by a doctor or a specially trained technician. To prepare for an ultrasound exam, wear clothes that allow your abdomen to be exposed easily.

You may need a full bladder for your exam.

As you lie on the table with your abdomen exposed from the lower part of the ribs to the hips, mineral oil or a gel is applied to the surface of the abdomen. This improves contact of the transducer with the skin surface.

When vaginal ultrasound is used, a condom ("rubber") is placed over a transducer before insertion into the vagina. Ultrasound with a vaginal probe is a painless exam that may feel like the exam you have for a Pap test.

Finally ... Combined with other tests and exams, ultrasound can help your doctor make an accurate diagnosis and determine proper treatment for certain problems.

This excerpt from ACOG's Patient Education Pamphlet is provided for your information. It is not medical advice and should not be relied upon as a substitute for visiting your doctor. If you need medical care, have any questions, or wish to receive the full text of this Patient Education Pamphlet, please contact your obstetrician-gynecologist.