What is an ultrasound?

An ultrasound is an imaging test that uses sound waves to make pictures (also known as a sonogram) of organs, tissues, and other structures inside your body. It allows your health care provider to see into your body without surgery.

Ultrasounds can help a provider:

• Monitor the health and development of a fetus during pregnancy. This may also be called a "prenatal ultrasound," "fetal ultrasound," or "obstetrical ultrasound." 
• Diagnose the cause of a wide variety of medical conditions. Ultrasound is best used to learn about conditions that involve soft tissues, such as organs, glands, and blood vessels. That’s because sound waves can more easily move through soft tissues.
• Guide certain biopsy procedures. Some biopsies use a needle to remove a sample of fluid or tissue from the body for testing. An ultrasound can find the abnormal area and guide the needle to the right place to collect the sample.

There are different types of ultrasounds. One type, called Doppler ultrasound, can show movement in your body. For example, it can show your heart beating and the speed and direction of blood flowing through your blood vessels. It can also show the beating heart and movement of a fetus.

Other types of ultrasounds can create 3-D (three-dimensional) or 4-D (three-dimensional and moving) images. These methods are more commonly used during the third trimester of pregnancy.

Other names: sonogram, ultrasonography, pregnancy sonography, fetal ultrasound, obstetric ultrasound, diagnostic medical sonography, diagnostic medical ultrasound

What is it used for?

An ultrasound can be used in different ways, depending on the type of ultrasound and which part of the body is being checked.

A pregnancy ultrasound may be used to:

• Check the size, position, heart rate, and age of the fetus.
• See if there is more than one fetus.
• Screen for: genetic disorders, such as Down syndrome, and birth defects in the heart, brain and spinal cord, or other parts of the body.
• Check the amount of amniotic fluid (the liquid in the sac surrounding a fetus) and the location of the placenta (the organ that brings oxygen and nutrients to the fetus). Some locations and positions of the placenta can cause pregnancy problems.
• See if your fetus is growing as expected.
• Guide the collection of test samples taken during amniocentesis and chorionic villus sampling (CVS).

A diagnostic ultrasound can help:

• Find the cause of pain, swelling, and other symptoms
• Rule out potential causes for your symptoms
• Look for blockages, growths, and structural problems in organs, glands, and blood vessels
• Tell the difference between cysts (fluid-filled sacs) and solid tumors

Ultrasound may help diagnose medical conditions that involve many parts of the body, such as the:

• Heart and heart valves
• Blood vessels
• Organs in the abdomen (belly), including the liver, gallbladder, pancreas, or spleen
• Organs in the pelvis, including the urinary tract, and male and female reproductive organs
• Thyroid and parathyroid glands
• Kidneys
• Breasts
• Brain, spine, and hips in infants

Why do I need an ultrasound?

If you're pregnant, it's common to have a routine ultrasound between weeks 18 and 22 of pregnancy to check on the health of your fetus. You may also need ultrasounds at other times during your pregnancy if you have:

• Symptoms of an ectopic pregnancy, which is when a fertilized egg tries to grow outside of the uterus. The egg cannot grow into a fetus when it's in the wrong place. It must be removed to avoid damage to your organs. This can be a medical emergency.
• Symptoms of a molar pregnancy, which is an abnormal growth of tissue in the uterus. It's caused by a fertilized egg with such severe genetic problems that it cannot become a fetus. The growth can turn into cancer and must be removed.
• A high-risk pregnancy (when you, your fetus, or both are at higher risk for health problems than in a typical pregnancy). This can happen if you have certain diseases or conditions such as high blood pressure, polycystic ovary syndrome (PCOS), obesity, and some autoimmune diseases.
• Any complications during your pregnancy. This can mean a change in your fetus' movement, abdominal pain that doesn't go away, heart palpitations, or extreme fatigue.

You may need a diagnostic ultrasound if you have signs or symptoms of certain types of medical conditions and your provider needs to look inside your body to help find the cause.

If you're having a needle biopsy to remove fluid or tissue for a test, you may have an ultrasound as part of the procedure.

What happens during an ultrasound?

An ultrasound is often done by a sonographer, a health care professional who has special training to do ultrasound exams. Ultrasounds may be done in different ways depending on the part of your body that's being examined. Most ultrasound exams include these general steps:

• You will remove clothing from the area that will be examined and lie on a table.
• The sonographer will spread a special gel on your skin over the area that will be examined.
• The sonographer will hold a wand-like device, called a transducer, and move it across your skin. The device sends sound waves into your body. The gel prevents air from getting between the device and your skin, which would block the soundwaves from entering your body. The sound waves are a very high pitch, so you can't hear or feel them.
• The soundwaves "bounce" off the structures inside your body. The ultrasound device picks up the echoes and turns them into images on a computer screen. You may be able to see the images on the screen during your exam.
• After the exam is over, the sonographer will wipe the gel off your skin.

For certain ultrasound exams, the ultrasound device is placed inside a body opening to get a clearer image. Depending on the organs being checked, the device may be placed in the:

• Vagina. This is called a transvaginal ultrasound. It helps view the uterus and ovaries.
• Rectum. This is called a transrectal ultrasound. It's usually done to view the prostate gland.
• Esophagus (the tube that connects your mouth and stomach). This is called a transesophageal echocardiogram (TEE). It's done to get clear images of the heart.

Will I need to do anything to prepare for the test?

Preparations for an ultrasound exam depend on what part of your body is being checked. Some ultrasound exams require no preparation at all. Your provider will tell you if you need to prepare for your ultrasound and what to do.

For example, if you're having an ultrasound to view your urinary tract, you may need to drink water so that you have a full bladder. You will have to hold your urine (pee) until the test is over. For other ultrasounds, you may need to fast (not eat or drink) for several hours before your test.

Are there any risks to the test?

Ultrasound has not been linked to any health harms. It's generally considered safe when trained sonographers use it correctly. Ultrasound doesn't use ionizing radiation like x-rays use, which makes it safer than x-ray. That's why ultrasound is the most widely used medical imaging method for viewing a fetus during pregnancy.

But in certain cases, ultrasound can affect fluids and tissues in the body. That's why most medical experts recommend using ultrasound only when it's needed to provide important medical information.

What do the results mean?

If your pregnancy ultrasound results were normal, it doesn’t guarantee you’ll have a healthy baby. No test can do that. But normal results may mean:

• Your fetus is growing at a normal rate.
• You have the right amount of amniotic fluid.
• No birth defects were found, though not all birth defects will show up on an ultrasound.

If your pregnancy ultrasound results were not normal, it may mean:

• The fetus is not growing at a normal rate.
• You have too much or too little amniotic fluid.
• You have an ectopic pregnancy.
• There is a problem with the position of the fetus in the uterus. This could make delivery more difficult.
• Your fetus has a birth defect.

If your pregnancy ultrasound results were not normal, it doesn’t always mean your fetus has a serious health problem. Your provider may suggest more tests to help confirm a diagnosis.

If you had diagnostic ultrasound, the meaning of your results will depend on which part of the body was being looked at.

If you have questions about your results, talk to your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

References

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The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.