Fetal Nuchal Fold Thickness Ultrasound (Nuchal Translucency or NT Scan)
A prenatal ultrasound screening test, usually performed between 11 and 14 weeks of pregnancy, that uses sound waves to measure the clear fluid space at the back of your developing baby's neck. All babies have some fluid in this area, but a larger-than-expected amount may suggest a higher chance of certain chromosomal conditions, such as Down syndrome, Edwards syndrome, or Patau syndrome. The scan is painless, safe for you and your baby, and typically takes about 15 to 30 minutes to complete.
{"A safe, painless ultrasound test performed between 11-14 weeks of pregnancy","Measures the clear fluid space (nuchal translucency) at the back of the baby's neck","Thicker than normal measurements may indicate higher risk for Down syndrome or other chromosomal conditions","This is a screening test, not a diagnostic test - follow-up testing is needed for confirmation","Often combined with blood tests for more accurate risk assessment"}
Key facts at a glance
- LOINC
- 12146-7
- Short code
- Fet Nuchal fold Thickness US.meas
- Synonyms
- Fet Nuchal fold Thickness US.meas
- Category
- cardiac
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 22
- Ref high
- 198
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- us-measured
- CPT
- 82553
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
The fetal nuchal fold thickness ultrasound (also called nuchal translucency or NT scan) is a prenatal screening test that uses sound waves to create images of the baby. It measures the clear fluid space at the back of the baby's neck. All babies have some fluid there, but babies with certain chromosomal conditions tend to have more fluid.
When is it done?
This test is typically performed between 11 weeks and 14 weeks of pregnancy. The timing is important because the nuchal fluid is most visible during this window and the baby is still small enough for clear measurements.
How is the test performed?
During the test, you will lie on an examination table. The ultrasound technician or doctor will apply a special gel on your abdomen and move a small device called a transducer over your belly. This device sends sound waves that create images of your baby on a screen. The test is completely painless and safe for both you and your baby. It usually takes about 15-30 minutes.
What do the results mean?
The results are reported as a measurement in millimeters (mm). A thicker than normal nuchal fold may indicate a higher risk for chromosomal conditions such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), or Patau syndrome (trisomy 13). However, a normal measurement does not guarantee a healthy baby, and an abnormal measurement does not mean your baby definitely has a problem. This is why it is called a screening test, not a diagnostic test.
Reference range
Adult males: 22-198 U/L; Females: 22-198 U/LN/A
No special preparation required. Inform provider of any chest pain or symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The nuchal fold thickness measurement is an important first-trimester screening tool. When combined with a blood test (measuring pregnancy-associated plasma protein-A and human chorionic gonadotropin), it forms the First Trimester Screening, which can detect approximately 80-85% of babies with Down syndrome. An increased nuchal fold measurement may also be associated with congenital heart defects, even when chromosomal testing is normal. If your results show an increased risk, your healthcare provider will discuss follow-up options with you, which may include diagnostic testing such as chorionic villus sampling (CVS) or amniocentesis.
Frequently asked questions
Does a thick nuchal fold mean my baby has Down syndrome?
Is the test safe for my baby?
Do I need to prepare for the test?
What happens if my results are abnormal?
Can I know the sex of my baby from this test?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy