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Nuchal Translucency Measurement (First Trimester Screening)

Published: August 9, 2026Updated: August 17, 2026

This test measures the fluid-filled space at the back of a baby’s neck during an early pregnancy ultrasound. It helps assess the risk of certain chromosomal conditions, such as Down syndrome, or other genetic abnormalities.

Quick summary

["Early pregnancy screening for potential genetic risks using ultrasound measurement."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
33069-6
Short code
Fet nuchal translucency US.meas
Synonyms
Fet nuchal translucency US.meas
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
7
Ref high
56
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-measured
CPT
84484
SNOMED
302773008
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 This Test Measures

The nuchal translucency (NT) is the amount of fluid visible under the skin at the back of your baby’s neck during a first-trimester ultrasound. This measurement is taken between 11 and 14 weeks of pregnancy. While the test itself doesn’t diagnose conditions, it provides important information for further evaluation if needed.

When and How It’s Done

A trained ultrasound technician performs this test during a routine prenatal ultrasound. You’ll lie on an exam table, and a gel is applied to your abdomen. A transducer (probe) is placed on your belly to create images of your baby’s neck region. The technician measures the NT thickness, which is recorded for review by your healthcare provider.

Why It Matters

The NT measurement is part of a first-trimester screening process that combines ultrasound findings with blood tests (like PAPP-A levels) to estimate the risk of chromosomal abnormalities. While not definitive, it helps guide decisions about additional testing if higher risk is identified.

What to Expect After the Test

After the ultrasound, you’ll typically return to your regular activities. Your healthcare provider will discuss the NT measurement results in relation to other screening factors, such as maternal age or blood test results, to determine if further genetic counseling or testing is recommended.

Reference range

Adult males: 7-56 U/L; Adult females: 7-43 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

The nuchal translucency test is a key part of first-trimester screening because an abnormally large NT may indicate an increased risk of chromosomal disorders like Down syndrome (trisomy 21) or other genetic conditions. It’s not a diagnostic test alone but often used alongside maternal blood tests (like nuchal translucency screening) to assess risk. If results suggest higher risk, additional genetic testing (e.g., amniocentesis or chorionic villus sampling) may be recommended to confirm or rule out conditions.

Short name

NT Scan

Frequently asked questions

How accurate is the nuchal translucency measurement?
The NT measurement is highly accurate when performed by trained professionals, but it’s part of a broader screening process. While it can identify some genetic risks, it’s not 100% precise. Your healthcare provider will consider the NT result along with other factors, such as maternal age, blood test results, and family history, to determine the overall risk.
What happens if my NT measurement is higher than expected?
A higher-than-expected NT measurement may signal an increased risk of certain chromosomal conditions. Your provider will discuss this with you and may recommend additional testing, such as a blood test (like PAPP-A) or genetic counseling. They’ll also explain the next steps, which could include further ultrasound evaluations or invasive procedures if needed.
Can I influence the NT measurement with lifestyle choices before the test?
While you can’t directly change the NT measurement, maintaining good prenatal health—such as avoiding smoking, limiting alcohol, and eating a balanced diet—can support overall pregnancy outcomes. However, the NT itself is primarily influenced by genetic and early developmental factors, not lifestyle choices at this stage.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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