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Nuchal translucency screening
Reviewed by the BabyCenter Medical Advisory Board
Last updated: April 2007
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Highlights
What is the nuchal translucency screening test?
What are the advantages of first-trimester screening?
How can I decide which tests are right for me?
How is the NT scan done?
How are the results computed?
What do the results mean?
How accurate is this test?
What if the results indicate that my baby is at high risk for a problem?
What is the nuchal translucency screening test?
This prenatal test (also called the NT or nuchal fold scan) can help your healthcare practitioner assess your baby's risk of having Down syndrome (DS) and some other chromosomal abnormalities as well as major congenital heart problems.
The NT test uses ultrasound to measure the clear (translucent) space in the tissue at the back of your developing baby's neck. Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester, causing this clear space to be larger than average.
The NT scan must be done when you're between 11 and 14 weeks pregnant. (The last day you can have it done is the day you turn 13 weeks and 6 days pregnant.) It's usually offered along with a blood test in what's known as first-trimester combined screening.
Like other screening tests, an NT scan won't give you a diagnosis. But it can assess your baby's risk for certain problems and help you decide whether you want to have chorionic villus sampling (CVS) or amniocentesis to find out whether your baby is actually affected.
The NT scan has been performed in the United States since 1995, mostly at large medical centers. Ultrasound technicians (sonographers) and doctors need special training and high-resolution ultrasound equipment to perform it correctly. They must be certified by the Fetal Medicine Foundation in London, the organization that sets the international standards and provides the software that enables a doctor to evaluate your baby's risk.
Because the NT scan requires special training and equipment, it's not yet available everywhere. But the test is being done more widely as more medical personnel get trained and certified. If you're interested, ask your healthcare practitioner or genetic counselor whether it's offere