Ultrasound is an imaging test that can be used for many different reasons. Ultrasound uses reflected sound waves instead of x-rays to create pictures of the internal organs. This makes it a safer alternative for internal images during pregnancy.

If you are pregnant, your doctor may recommend this procedure for you. Here is some information on the types and uses of ultrasound, and what you can expect if you have one.

It is not necessary for every pregnant woman to have ultrasound. However, it is an excellent way to determine the age of the fetus if the dates of the last menstrual period are not known. The procedure is often used, along with a medical history and physical exams, to screen for problems or monitor a condition. Your healthcare provider will discuss with you the use of ultrasound to monitor your pregnancy.

Ultrasound helps to determine whether the fetus is growing properly. If there is an abnormality, your healthcare provider may be able to help you reduce risks to yourself and the growing fetus. Ultrasound is used to detect:

A vaginal ultrasound is similar the above ultrasound, but the ultrasound probe is inserted into the vagina rather than placed on the abdomen. Vaginal ultrasound is used to:

Doppler ultrasound provides sound that can be heard through amplification. It is used to monitor the fetal heartbeat before or during labor. It is also used to measure the flow of blood within the vessels of the uterus, umbilical cord, and fetus.

To prepare for the exam, you should wear comfortable clothes. You may be asked to wear a hospital gown. If you are having a vaginal ultrasound, you will need to remove your clothes from the waist down and cover up with a sheet. Abdominal ultrasound exams may require a full bladder to help the clinician view the pelvic organs. If this is the case, you will be asked to drink several glasses of water before the exam and not urinate until the exam is over.

With most ultrasound exams, you will lay on the table with your abdominal area exposed. A thin gel will be applied to your abdomen, which improves contact with the transducer. The transducer will be moved along your abdomen, sending out sound waves that are reflected back from the organs and fetus.

No harmful effects have been found from ultrasound since it was first used over 40 years ago. There are no known long-term risks for mother or baby. The benefits are that it is accurate and fast in detecting problems and does not involve the use of radiation, drugs, chemicals, or dyes.

Talk to your doctor about the potential risks and benefits before having the exam.

Last Reviewed December 2012