Most often, a nuchal translucency test is done by a specially trained ultrasound technologist. But it may be done by a radiologist or an obstetrician who has received special training to do this test.

Often you don't need to remove your clothes for the test, or you'll be given a gown to wear.

If you need a full bladder for the test, tell your doctor or ultrasound technologist if your bladder is so full that you're in pain.

For an abdominal ultrasound:

• You'll lie down on your back or on your side on an examination table.
• A gel will be spread on your belly.
• A small, hand-held device called a transducer will be pressed against the gel on your skin and moved over your belly. Images of the baby are displayed on a monitor. The technologist or doctor will look for and measure the thickness of the fluid buildup at the back of the baby's neck.

When the test is done, the gel is wiped off your skin. You can urinate as soon as the test is done.

For a transvaginal ultrasound, a small transducer will be inserted into your vagina.

How long the test takes

The test usually takes about 15 to 20 minutes.

During a nuchal translucency test, you may have a feeling of pressure in your bladder.

For an abdominal ultrasound, the gel may feel cool when it is first put on your belly. You'll feel a light pressure from the transducer as it passes over your belly.

For a transvaginal ultrasound, you may feel some pressure when the transducer is in your vagina.

There are no known risks linked with a nuchal translucency test, either to you or the baby. But you may feel anxious if the test shows that there's an increased chance that your baby may have a problem.

Ultrasound is a safe way to check for problems and get information about your developing baby. It doesn't use X-rays or other types of radiation that may harm the baby.

Your doctor will look at the results of the nuchal translucency test to see if the area at the back of the baby's neck is thicker than normal.

You may not receive information about the test right away. Full results are usually ready in 1 or 2 days.

How accurate is the test?

The test can find out if your developing baby (fetus) is at higher-than-normal risk for problems. But it can't tell for sure that the baby has a problem. You would need another test, called a diagnostic test, to make sure.

The accuracy of this test is based on how often the test correctly finds a problem. For example:

• The nuchal translucency test correctly finds Down syndrome in 64 to 70 out of 100 fetuses who have it. It misses Down syndrome in 30 to 36 out of 100 fetuses.^{footnote 1}

It's possible that a screening test will show that the baby has an increased chance of having a problem when he or she doesn't have the problem. This is called a false-positive test result. And it's also possible that a screening may show that the baby doesn't have a problem when he or she does. This is called a false-negative test result.