Why is a nuchal translucency screening test done?
A nuchal translucency test is done to find out the chance that your developing baby (fetus) may be at risk for having Down syndrome or other problems.
How is a nuchal translucency screening test done?
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 midwife 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 exam table.
- A gel will be spread on your belly.
- A small, handheld 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 or midwife 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 do you prepare for a nuchal translucency screening test?
You may need a full bladder for the nuchal translucency test. If so, you'll be asked to drink water or other liquids just before the test and to not urinate before the test.
What do the results of a nuchal translucency screening test mean?
Your doctor or midwife 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 about 70 out of 100 fetuses who have it. It misses Down syndrome in about 30 out of 100 fetuses.
It's possible that a screening test will show that the baby has an increased chance of having a problem when the baby 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 the baby does. This is called a false-negative test result.
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