by Scholten A

What Is Ultrasound?

image for pregnancy 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 internal organs. This makes it a safer alternative for internal images during pregnancy.

If you are pregnant, it is likely that you will have at least one ultrasound.. Here is some information on the types and uses of ultrasound, and what you can expect.

How Is Ultrasound Used During Pregnancy?

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 in you or your fetus. Ultrasound can help 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.

Your healthcare provider will discuss with you the use of ultrasound to monitor your pregnancy. Ultrasound may be used to detect:

  • The number of fetuses
  • The age of the fetus
  • The size of the fetus and rate of growth
  • The heart rate, breathing, position, and movement of the fetus
  • The location of the placenta
  • The amount of amniotic fluid in the uterus
  • Certain types of birth defects, including some that affect the heart, head, chest, spine, and limbs

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:

  • Detect an ectopic pregnancy
  • Determine the cause of bleeding or pain
  • Assess the length of the cervix if there is concern that it is short
  • Detect certain birth defects early in the pregnancy

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

What Happens During an Ultrasound Exam?

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.

Are There Any Risks Associated With Ultrasound?

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.


Family Doctor—American Academy of Family Physicians 

The American Congress of Obstetricians and Gynecologists 


Health Canada 

Women's Health Matters 


Prenatal care and tests. Office on Women's Health website. Available at: Updated September 27, 2010. Accessed October 21, 2016.

Prenatal ultrasound testing. EBSCO DynaMed Plus website. Available at: . Updated February 5, 2016. Accessed October 21, 2016.

Ultrasound exams. The American College of Obstetricians and Gynecologists website. Available at: Updated September 2013. Accessed October 21, 2016.

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