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Nuchal translucency test

Show Alternative Names
Nuchal translucency screening
NT
Nuchal fold test
Nuchal fold scan
Prenatal genetic screening
Down syndrome - nuchal translucency

The nuchal translucency test measures the nuchal fold thickness. This is an area of tissue at the back of an unborn baby's neck. Measuring this thickness helps assess the risk for Down syndrome and other genetic problems in the baby.

How the Test is Performed

Your health care provider uses abdominal ultrasound or a vaginal ultrasound to measure the nuchal fold. All unborn babies have some fluid at the back of their neck. In a baby with Down syndrome or other genetic disorders, there is more fluid than normal. This makes the space look thicker.

A blood test of the mother is also done. Together, these two tests will tell if the baby could have Down syndrome or another genetic disorder.

How to Prepare for the Test

Having a full bladder will give the best abdominal ultrasound picture. You may be asked to drink 2 to 3 glasses of liquid an hour before the test. DO NOT urinate before your ultrasound.

If a vaginal ultrasound is performed, your bladder should be empty.

How the Test will Feel

You may have some discomfort from pressure on your bladder during the ultrasound. The gel used during the test may feel slightly cold and wet. You will not feel the ultrasound waves.

Why the Test is Performed

Your provider may advise this test to screen your baby for Down syndrome. Many pregnant women decide to have this test.

Nuchal translucency is usually done between the 11th and 14th week of pregnancy. It can be done earlier in pregnancy than amniocentesis. Amniocentesis is another test that checks for birth defects.

Normal Results

A normal amount of fluid in the back of the neck during ultrasound means it is very unlikely your baby has Down syndrome or another genetic disorder.

Nuchal translucency measurement increases with gestational age. This is the period between conception and birth. The higher the measurement compared to babies the same gestational age, the higher the risk is for certain genetic disorders.

A measurement of up to 3 mm is considered a low risk for genetic disorders. However, different clinics may use slightly different numbers based on their experience.

What Abnormal Results Mean

More fluid than normal in the back of the neck means there is a higher risk for Down syndrome, trisomy 18, trisomy 13, Turner syndrome, or congenital heart disease. But it does not tell for certain that the baby has Down syndrome or another genetic disorder. A diagnostic test is required to find out if a serious genetic disorder is present.

The nuchal translucency test is a screening test. It does not screen for genetic problems in babies. It is helpful in deciding who may need further testing. An abnormal result would then require follow up of a diagnostic test such as an amniocentesis or non-invasive prenatal test (NIPT).

Risks

There are no known risks from ultrasound.

Review Date: 6/5/2023

Reviewed By

John D. Jacobson, MD, Professor Emeritus, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

References

American College of Obstetricians and Gynecologists website. NIPT summary of recommendations. www.acog.org/advocacy/policy-priorities/non-invasive-prenatal-testing/current-acog-guidance. Accessed June 7, 2023.

Driscoll DA, Simpson JL. Genetic screening and diagnosis. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 10.

Dugoff L, Wapner RJ. Prenatal diagnosis of congenital disorders. In: Lockwood CJ, Copel JA, Dugoff L, et al, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 9th ed. Philadelphia, PA: Elsevier; 2023:chap 30. 

Walsh JM, D'Alton ME. Nuchal translucency. In: Copel JA, D'Alton ME, Feltovich H, et al, eds. Obstetric Imaging: Fetal Diagnosis and Care. 2nd ed. Philadelphia, PA: Elsevier; 2018:chap 45.

Disclaimer

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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Ultrasound - Animation

Ultrasound is one of the most useful procedures for monitoring a baby's prenatal development. With ultrasound, doctors can check for defects of the head, spine, chest, and limbs; diagnose serious conditions like placenta previa or breech birth; and check to see whether the mother will have twins or triplets.

Ultrasound can be used anytime during pregnancy from the fifth week until delivery. It uses inaudible sound waves to "see" the baby inside the uterus. These sound waves bounce off solid structures in the body and are transformed into an image on a screen.

Here's how ultrasound works. Pretend this tennis ball is an organ in the body. This piece of glass represents the ultrasound image. Like this piece of glass, an ultrasound image is actually flat and two-dimensional.

If we could pass this tennis ball through the glass, the ultrasound image would show wherever the two are in contact. Let's watch the same thing on an ultrasound.

The white ring is the reflected image of the outer part of the tennis ball. Like many organs in the body, the tennis ball is solid on the outside, and hollow on the inside. Solid structures, like bones and muscles, reflect sound waves that show up as light gray or white images.

Soft or hollow areas like the chambers of the heart don't reflect sound waves. So they show up as dark or black areas.

In an actual ultrasound of a baby in the uterus, the solid structures in the baby’s body are transmitted back to the monitor as white or gray images. As the baby moves back and forth, the monitor shows the outline of his head. The eyes show as dark spots in the head. The region of the brain and the heart are also shown.

Remember, ultrasound only shows a flat image of the baby. A superimposed illustration of the fetus shows how the fetus actually looks in the uterus.

Ultrasound is still one of the best methods for physicians to visually diagnose major physical defects in the growing baby.

Even though there are no known risks for ultrasound at present, it is highly recommended that pregnant women consult their physician before undergoing this procedure.

 

Ultrasound - Animation

Ultrasound is one of the most useful procedures for monitoring a baby's prenatal development. With ultrasound, doctors can check for defects of the head, spine, chest, and limbs; diagnose serious conditions like placenta previa or breech birth; and check to see whether the mother will have twins or triplets.

Ultrasound can be used anytime during pregnancy from the fifth week until delivery. It uses inaudible sound waves to "see" the baby inside the uterus. These sound waves bounce off solid structures in the body and are transformed into an image on a screen.

Here's how ultrasound works. Pretend this tennis ball is an organ in the body. This piece of glass represents the ultrasound image. Like this piece of glass, an ultrasound image is actually flat and two-dimensional.

If we could pass this tennis ball through the glass, the ultrasound image would show wherever the two are in contact. Let's watch the same thing on an ultrasound.

The white ring is the reflected image of the outer part of the tennis ball. Like many organs in the body, the tennis ball is solid on the outside, and hollow on the inside. Solid structures, like bones and muscles, reflect sound waves that show up as light gray or white images.

Soft or hollow areas like the chambers of the heart don't reflect sound waves. So they show up as dark or black areas.

In an actual ultrasound of a baby in the uterus, the solid structures in the baby’s body are transmitted back to the monitor as white or gray images. As the baby moves back and forth, the monitor shows the outline of his head. The eyes show as dark spots in the head. The region of the brain and the heart are also shown.

Remember, ultrasound only shows a flat image of the baby. A superimposed illustration of the fetus shows how the fetus actually looks in the uterus.

Ultrasound is still one of the best methods for physicians to visually diagnose major physical defects in the growing baby.

Even though there are no known risks for ultrasound at present, it is highly recommended that pregnant women consult their physician before undergoing this procedure.

 
 
 
 

 

 
 
 
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