Patient guide · Fetal medicine
Nuchal translucency scan, 11-13+6 week ultrasound measurement of the fluid at the back of the fetal neck.
The nuchal translucency (NT) scan measures a small pocket of fluid at the back of the fetal neck between 11+2 and 13+6 weeks. Combined with maternal blood tests (PAPP-A, β-hCG) it forms the combined first-trimester screen for trisomies 21, 18 and 13.
Key facts
- 01
What it is
Fetal nuchal translucency (NT) measurement performed by ultrasound between 11+2 and 13+6 weeks of pregnancy.
- 02
Combined screen
Combined with maternal serum PAPP-A and free β-hCG to calculate risk for trisomies 21, 18 and 13.
- 03
Who performs it
Requires an accredited fetal medicine sonographer working to Fetal Medicine Foundation criteria.
- 04
When NT is raised
An NT greater than 3.5 mm is associated with cardiac anomalies, other structural defects and genetic syndromes.
- 05
Complementary to NIPT
NIPT offers higher sensitivity for common trisomies; NT still assesses fetal anatomy and cardiac risk.
- 06
Basis for further tests
Findings guide decisions about chorionic villus sampling (CVS) or amniocentesis.
How it works
From booking to result — what happens, in order.
The pathway is short. The measurement is precise. The interpretation is done by a fetal medicine team.
- 01
Before
Book at 11-13+6 weeks
The NT window is narrow. Booking is timed by crown-rump length (CRL) between 45 and 84 mm.
- 02
Before
Full bladder for the scan
A moderately full bladder helps visualise the uterus on transabdominal ultrasound.
- 03
On the day
NT measured to strict criteria
Mid-sagittal view, fetus neutral, image magnified so head and upper thorax fill the screen; calipers placed on-to-on.
- 04
On the day
Advanced markers added
Nasal bone presence, ductus venosus flow and tricuspid regurgitation improve risk estimation where offered.
- 05
On the day
Combined risk calculated
NT, maternal age, PAPP-A and β-hCG combine into a single trisomy risk figure.
- 06
After
Written report and counselling
Results are delivered with a fetal medicine consultation to explain risk, options and next steps.
- 07
After
A structured plan
Reassurance, NIPT, CVS, amniocentesis or fetal medicine follow-up — chosen with you, not for you.
What it shows
What the NT scan can — and can’t — tell you.
A single fluid measurement, blended with maternal bloods and advanced markers, into one combined risk figure.
-
NT measurement
The pocket of fluid at the back of the fetal neck, measured in millimetres.
-
Combined trisomy risk
A single figure for trisomies 21, 18 and 13, combining NT with maternal bloods.
-
Cardiac anomaly risk (NT > 3.5 mm)
A raised NT flags increased risk of major congenital heart disease.
-
Nasal bone presence
Absent nasal bone is associated with an increased risk of trisomy 21.
-
Ductus venosus flow (advanced)
Abnormal a-wave in the ductus venosus refines trisomy and cardiac risk.
-
Tricuspid regurgitation (advanced)
Tricuspid regurgitation on Doppler further modifies risk estimates.
-
Structural anomalies (major)
Major fetal anomalies visible at 12 weeks — anencephaly, abdominal wall defects, cystic hygroma.
-
Red flag: NT > 3.5 mm — fetal medicine + fetal echo referral
A raised NT triggers fetal medicine referral and specialist fetal echocardiography.
Options
What can follow an NT scan.
The next step depends on your combined risk, the anatomy seen and — always — what you want.
-
Reassurance if low risk
A low combined risk allows routine antenatal care to continue without additional testing.
-
NIPT for higher-sensitivity screen
Non-invasive prenatal testing on maternal blood offers > 99% sensitivity for trisomy 21.
-
CVS 11-13 weeks
Chorionic villus sampling gives a diagnostic karyotype and microarray in the first trimester.
-
Amniocentesis from 15 weeks
Diagnostic testing on amniotic fluid from 15+0 weeks onwards.
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Fetal medicine MDT
Complex findings are reviewed by a multi-disciplinary fetal medicine team.
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Fetal echocardiogram (NT > 3.5 mm)
Detailed cardiac ultrasound at 18-22 weeks — earlier if indicated.
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Postnatal paediatric planning
Coordinated planning with neonatology and paediatric sub-specialties before delivery.
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Bereavement pathway if applicable
Compassionate, specialist-led support if the pregnancy cannot continue.
Red flags
When findings should prompt fetal medicine referral.
Any of these findings should trigger onward referral to a fetal medicine consultant for detailed assessment and counselling.
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NT > 3.5 mm
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Absent nasal bone
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Abnormal ductus venosus flow
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Tricuspid regurgitation
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Cystic hygroma
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Combined trisomy risk > 1:150
-
Structural fetal anomaly
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Family history of chromosomal condition
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Consanguinity
Sources
The guidance behind this page.
Reviewed against UK and international fetal medicine guidance. Next scheduled review: 2027-07-30.
Frequently asked
Everything we get asked about the NT scan.
Timing, safety, what a raised NT means, and how NT and NIPT fit together.
-
What is a nuchal translucency scan?
An ultrasound performed between 11+2 and 13+6 weeks of pregnancy that measures the small pocket of fluid at the back of the fetal neck. Combined with maternal blood tests (PAPP-A and free β-hCG) it forms the combined first-trimester screen for trisomies 21, 18 and 13.
-
Is the NT scan the same as the 12-week scan?
The dating scan is offered around 11-14 weeks to confirm viability and estimate the due date. The NT scan is performed in the same window but adds a specific fluid measurement and combined trisomy risk. Many clinics offer them together.
-
What does a raised NT mean?
An NT above 3.5 mm is associated with an increased risk of chromosomal conditions, congenital heart disease and other structural anomalies. It does not confirm a diagnosis — it prompts fetal medicine referral, detailed anatomy scans and diagnostic testing such as CVS or amniocentesis.
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Should I have NIPT or an NT scan?
They answer different questions. NIPT has higher sensitivity for common trisomies but does not look at fetal anatomy. NT assesses NT thickness, early anatomy and cardiac risk. Many women have both — NT for structure and NIPT for chromosomal precision.
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Is the scan safe?
Yes. Diagnostic ultrasound uses sound waves, not radiation, and has an excellent safety record throughout pregnancy.
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What happens if the combined risk is high?
You will be offered a consultation with a fetal medicine consultant to discuss NIPT (if not already done), diagnostic testing (CVS or amniocentesis), further imaging, and the practical and emotional implications of each option.
Related tests
Explore other first-trimester tests.
-
First trimester dating scan
Confirms viability and estimates your due date at 11-14 weeks.
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NIPT
Non-invasive prenatal test with high sensitivity for common trisomies.
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Amniocentesis
Diagnostic testing on amniotic fluid from 15+0 weeks.
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In practice, in London
Getting nuchal translucency scan sorted in London, without the guesswork
With nuchal translucency scan, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. On the NHS, nuchal translucency scan typically sits behind a triage step and a wait that can stretch from a few weeks into months. In London’s private sector, the same appointment often lands within days. That speed matters when symptoms are disrupting work, sleep, or a plan you’d already committed to — and it’s the single most common reason people call us in the first place.
A private nuchal translucency scan pathway in London usually looks like this: an initial consultation, any diagnostics booked at a nearby facility (most within Zone 1 or 2), and a written report sent to you and your GP within a few days. The consultants we work with hold NHS posts alongside their private lists, which keeps the standards consistent across both settings. For nuchal translucency scan specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
We’re careful about what a private pathway for nuchal translucency scan can and can’t promise. It can compress a wait, put you in front of a subspecialist quickly, and get a proper report in your hands within a week. It can’t rewrite what the imaging or the bloods say. Setting that expectation up front tends to make the whole experience less stressful.