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Nuchal Translucency (NT): Past, Present and Future.

I qualified as an obstetrician in 1987 and was immediately drawn to ultrasound. My first machine had a small green screen, but it showed a living baby and that image stayed with me. Since then I have scanned almost every day for nearly four decades and watched the field transform: Doppler, fetal echocardiography, transvaginal scanning, and neurosonography. From the late 1990s I focused on very early diagnosis of fetal anomalies. I moved detailed anatomy from 14–16 weeks to 12–13 weeks, and more recently to 10–11 weeks. That shift was practical, not fashionable. Earlier scanning gives clearer next steps, earlier testing, and calmer decisions for families.

Story of NT

The story of nuchal translucency began in London. In 1992 Professor Kypros Nicolaides and colleagues described a reliable way to measure the fluid behind the fetal neck (nuchal translucency or NT) and showed that a thicker NT was linked to poorer outcomes, especially chromosomal anomalies. The Combined Screening Test, NT with PAPP‑A and hCG, followed soon after. In 1996 the Fetal Medicine Foundation lead by Prof Nicolaides set standard methods for measuring NT between 11 and 14 weeks.

Very quickly it became clear that NT was not only about trisomy 21. Many structural, chromosomal and single‑gene conditions could present with a large NT. The idea turned the spotlight onto the first trimester and changed what we looked for in everyday practice.

Historically, many early papers on increased NT focus on NT at 10 weeks, and their illustrations depict very young fetuses, 10-11 weeks with NT measured in CRL plane. Current literature shows that this approach was correct, and that NT at 10 weeks probably has higher clinical value than at later stages, because more than 40% of fetuses (!) with increased NT ≥ 2.5 mm have a poor outcome.

Why, then, did 10‑week NT fall out of favour after the promising early papers of the 1990s? Three reasons stand out. First, standardisation was difficult. A 30‑mm fetus at 10 weeks does not image like an 84‑mm fetus at 14 weeks; you cannot expect identical pictures across the window. Second, the machines of that era struggled at 10 weeks. Even severe anomalies could be missed. Third, there was no actionable pathway. NIPT did not exist, and CVS before 11 weeks was impractical, so a measurement at 10 weeks rarely changed care.

Those barriers have largely gone. We can change the NT measurement criteria and use the original mid‑sagittal whole‑body image (CRL view) to calculate NT at 10 weeks. Trained professionals using modern scanners can detect major anomalies with confidence at that stage. Advanced NIPT, including options for single‑gene disorders, is available from 10 weeks. In this setting, 10‑week NT regains its clinical value. It is not a verdict; it is a signal to move thoughtfully and early.

NIPT and NT

Non invasive prenatal testing (NIPT altered the landscape of NT and CST. The first commercial test appeared in 2011. By analysing cell‑free DNA in maternal blood, largely placental in origin, it assesses genotype rather than indirect Combined Screening Test (CST) markers. For trisomy 21, performance is superior to the CST, with far fewer false positives and a very high negative predictive value. It also allows earlier screening. These advantages led countries such as the Netherlands and Belgium to adopt first‑line NIPT, while the UK introduced contingent NIPT after a high‑chance Combined Screening Test, reducing unnecessary invasive procedures. None of this removes the value of NT; it reshapes how we use it. 

NT and me: 10 practical lessons

My relationship with NT is long and personal. I met my first case of markedly increased NT in 1993, less than one year after its original description by Prof Nicolaides. I still remember the patient, the room, and the hydropic appearance on the screen. Years later, in 2010, I joined the Fetal Medicine Unit at UCLH in London and concentrated on head‑to‑toe fetal assessment at 11–13 weeks, paying particular attention to the tiny fetal heart. I saw most referrals with raised NT. Many of these women were frightened; I never forgot that. Over the years, at UCLH and subsequently in private practice, I have scanned more than 1,000 fetuses with NT ≥ 3.5 mm. The largest NT I have seen measured 25 mm.

I have been deeply involved in training clinicians to perform first-trimester scans and NT assessment and management. My instructional videos: "Nuchal translucency (NT)", "Increased Nuchal Translucency", and others, published on YouTube in the early 2010s, have amassed over two million views. I created the "NT Expert" course on the challenges of NT assessment and management and have delivered it internationally.

What did those years teach me? Those are 10 lessons:

1. Many babies with increased NT are healthy. A raised measurement increases risk, but it does not label a child.
2. A raised NT signals a present issue. It may resolve or it may predict serious disease, but it is not a reason to wait. The correct response is a prompt, expert, head‑to‑toe scan - days, not weeks, after the finding.
3. While trisomies 21 and 18 are frequent, they are not the whole story. Rare chromosomal defects, single‑gene syndromes, structural anomalies, and copy‑number variants (microdeletions and microduplications) make up a large share of the pathology.
4. One point concerns the heart. When raised NT accompanies an isolated cardiac defect, the defect is usually severe and is often visible at 12–13 weeks. Early fetal echocardiography is warranted immediately and should not be delayed until 16–20 weeks.
5. The best predictor of outcome is the expert scan performed before CVS. Most chromosomal or genetic disorders leave clues on careful imaging if we are prepared to look. CVS will confirm the phenotype findings.
6. A normal early scan does not exclude many single‑gene disorders. Noonan and Sotos syndromes, or spinal muscular atrophy, may show very little at that stage.
7. A normal NT is reassuring, not protective. The majority of serious problems can coexist with a normal NT, so we must never use a single number as a shield.
8. The timing of NIPT matters. Performed at 12-13 weeks, it often pushes diagnosis towards 14–16 weeks and delays CVS or even amniocentesis.
9. Our current pathways are somehow structured to support delayed diagnosis and remain incomplete. Structural problems, especially cardiac, are often recognised only at the 20‑week scan rather than at 12-13 weeks early echocardiography. Learn how to scan the heart earlier.
10. When NT is raised, the diagnostic work‑up should include testing for monogenic conditions. A microarray is essential but not sufficient; monogenic NIPT or exome sequencing is required. Otherwise, monogenic disorders may go undetected if imaging is not integrated with genetics. A baby with a genetic disorder can be born after "reassuring" results from invasive testing.

10 Week Scan and NIPT

In May 2020, at the beginning of the first COVID lockdown, we opened the London Pregnancy Clinic (LPC). The goal was simple: a one‑stop visit that brought a high‑quality early anatomy scan together with NIPT. We began at 12 weeks, but the timing blunted the advantage of NIPT. Moving the scan and blood draw to 10 weeks changed everything. My experience with 10‑week scanning dated back to the 2000s, so building a structured protocol was natural. After several thousand cases and the training of colleagues, the strengths are clear: earlier answers, better targeting of tests, and fewer long waits.

Ultrasound and NIPT answer different questions and work synergistically. The scan shows the phenotype; NIPT explores the genotype. Used together at 10 weeks they create a workable path. A woman attends for a 10 Week Scan by a specially trained professional. The aim of the scan is to do thorough examination of fetal anatomy by our protocol and to measure NT. We take blood for NIPT the same day, tailored to the findings and the family. If results or anatomy point to a specific cause, we proceed to CVS with the right test in hand. This pace respects both the biology and the family.

We developed the SMART Test® to formalise that approach. It is not a new molecule or a boutique brand. It is a structured way to bring the 10‑Week Scan and modern NIPT together, and to add targeted diagnostics when needed. The aim is simple: detect serious structural, chromosomal, and monogenic conditions early and accurately, while keeping communication clear and humane.

SMART NT protocol: The solution for early increased NT

What exactly do I suggest, and why is the protocol called SMART NT? It is a streamlined variant of our LPC SMART Test® for fetuses with increased NT at 10 weeks.

What is the problem with the current NT approach? There is a timing gap: NIPT can be done at 10 weeks, while conventional NT measurement is usually performed around 12 weeks. This gap erodes the advantages of NIPT. A second issue is that, when NT is increased, the CVS usually offered is invasive but often limited in scope, as the standard analysis focuses on PCR/karyotype/microarray rather than targeted single-gene testing. So CVS is usually geared to chromosomes and microdeletions/microduplications rather than monogenic disorders. Advanced NIPT, such as KNOVA, PrenatalSafe Complete Plus or Vistara plus extended Panorama, may offer a real advantage for high‑NT cases linked to monogenic conditions compared with routine CVS plus PCR/microarray.

What does this mean in practice?

Step One: Scan at 10 weeks to exclude major, usually non‑genetic anomalies such as acrania and body‑stalk anomaly, and obtain a standardised NT using the 10‑week protocol. If NT is ≥ 2.5 mm, use an advanced NIPT that covers carefully selected common and rare chromosomal conditions, key microdeletions, and an extended monogenic panel strongly associated with increased NT. At present, the best option is KNOVA by Fulgent. The typical turnaround time is about two weeks, during which the fetus will grow and develop.

Step Two: When the NIPT result is back (high chance or low chance) at 12-13 weeks, perform a targeted scan with early fetal echocardiography and document NT dynamics (rising, stable, or resolving). If NIPT flags a chromosomal or genetic condition, the scan should attempt phenotyping before proceeding to CVS. If NIPT indicates low probability, the scan should screen carefully for structural anomalies associated with increased NT.

The best outcome is a low‑chance KNOVA result, resolution of the NT, and no structural abnormalities on target scan. Understandably, there is still a need for a 20-week anomaly scan, and although genetic or chromosomal conditions are very unlikely, they cannot be completely excluded.

Conclusions

The SMART NT protocol already addresses the majority of problems associated with increased NT at the time when the patient is planning to attend her standard first 12‑week nuchal scan. It screens for a wide range of structural, chromosomal and single‑gene disorders associated with high NT and is entirely safe. In the case of high‑chance NIPT, diagnostic testing (CVS) can be done at the right time.

It is estimated that around 1.4 million babies worldwide each year have an NT in abnormal range. Unfortunately, we are not able to respond personally to every individual case, so this website is designed to provide general information and guidance rather than case-specific advice.

We provide training and support for other professionals. Join our SMART NT network now. 

Disclaimer

These reflections are my own and arise from practice rather than committee. They do not represent the positions of the FMF, UCLH, NHS, RCOG, ISUOG, or any other organisation. As with any clinician, I may make mistakes or misjudgements. But I believe that coupling a careful 10 Week Scan with modern NIPT, and escalating to targeted diagnostics when indicated, offers families the balance we seek: early clarity without haste, and precision without noise.

Dr Fred Ushakov

London, 20 November 2025