Patients

No. The NHS does not routinely perform formal NT measurements at 10 weeks. In the NHS screening programme, NT is measured as part of the combined test only when the baby’s crown–rump length is 45–84 mm, which corresponds to about 11 weeks and 2 days to 14 weeks and 1 day of pregnancy.

A blood sample for combined screening can be taken from 10 weeks, but the ultrasound NT measurement itself is not part of the standard NHS pathway at that stage. Some parents may have an earlier viability or dating scan around 10 weeks, and a clinician may notice increased fluid, but this is outside the routine NHS NT screening window.

No. In the UK, there is no specific national requirement to perform a formal NT assessment or automatic referral before the standard NHS combined screening window. Within the NHS screening programme, NT is used as part of the combined test only once the baby is large enough for a validated measurement, which is generally from 11 weeks plus 2 days onwards (CRL 45 mm and more). Before that point, there is no established national pathway for early increased NT, and NT should not be interpreted in the same formal way as it is at the routine 11–14 week scan.

In practice, this means that communication can be variable. If a sonographer or doctor sees a possible increase in fluid behind the baby’s neck before 11 weeks, they may decide not to present this as a formal abnormal NT finding, particularly when there is no NHS protocol, no clear referral route, and the standard plan would usually be repeat assessment at the routine 12-week scan. Some clinicians may feel that raising the issue too early could create significant anxiety for parents at a stage when the finding may still be uncertain and when formal screening criteria have not yet been met. This is better described as cautious or inconsistent early disclosure, rather than a defined rule not to tell parents.

That said, doctors still have a general professional duty to communicate relevant information honestly and to support informed decision-making. So while there may be no specific obligation to disclose “increased NT” before 11 weeks as a formal screening diagnosis, there is still an ethical expectation to be open if a potentially important concern is seen, especially if parents ask directly about the appearance of the scan. In those situations, clinicians may explain that the finding is not yet part of the validated NHS NT pathway, but that there appears to be increased fluid or a possible early concern that should be reassessed.

SMART NT is a specialised adaptation of the SMART Test® for pregnancies in which increased NT is identified at 10 weeks. The SMART NT protocol is designed specifically for the management of early increased NT and includes confirmation of increased NT (above 2.5 mm), KNOVA NIPT, and a detailed follow-up targeted scan at 12–13 weeks. SMART Test® is a registered trademark of London Pregnancy Clinic.
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If your baby’s NT is normal at 10 weeks, this is very good news. You can still choose further testing for added peace of mind through the SMART Test®. SMART Test® combines an advanced 10-week scan with an extended NIPT panel, and London Pregnancy Clinic currently offers SMART Test® KNOVA and SMART Test® Plus as part of this pathway.

Unlike SMART NT, the standard SMART Test® does not routinely include an early follow-up fetal scan, although this can be arranged separately. In this situation, we would usually recommend an Early Fetal Scan slightly later, at around 14–16 weeks, when the baby’s anatomy is more developed and a wider range of structural abnormalities can be assessed.

KNOVA is an important part of the assessment, but it does not replace specialist ultrasound. While KNOVA can screen for selected chromosomal and monogenic conditions associated with increased NT, only expert scanning can assess the baby’s anatomy and look for major structural abnormalities, including early signs of congenital heart disease.

At London Pregnancy Clinic (LPC), both scans play a distinct and valuable role. The 10 Week Scan helps exclude major and potentially lethal structural abnormalities that may not be linked to a detectable genetic syndrome. The 12–13 week targeted scan (Early Fetal Scan and Early Echocardiography) provides a more detailed anatomical review, with particular attention to abnormalities associated with increased NT, especially cardiac defects.

Although these scans can be delayed and performed later within the NHS or elsewhere, early specialist assessment may identify an underlying structural cause much sooner. If increased NT is related to a structural problem, it is often more helpful to detect this on an expert targeted scan at the earliest possible stage, rather than waiting for it to declare itself later in pregnancy.

A 10-week specialist scan does not replace the routine NHS 12-week scan, but it can provide important information earlier. In the NHS, formal NT measurement is part of the combined screening pathway only when the baby’s crown–rump length is 45–84 mm, which corresponds to about 11 weeks and 2 days to 14 weeks and 1 day. By contrast, the national NHS pathway for structural anomaly screening is the 20-week anomaly scan, performed between 18+0 and 20+6 weeks, when the baby is screened for 11 physical conditions.
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This means the routine NHS 12-week scan does check NT, but it is not the national screening pathway for detailed structural assessment of the fetus. Some NHS units do look carefully at early fetal anatomy at 12 weeks, and obvious severe abnormalities may sometimes be suspected at that stage, but this is not the same as a nationally standardised first-trimester anomaly screening programme.

For that reason, an earlier specialist scan at 10 weeks may be helpful if you want information sooner rather than waiting for the routine NHS pathway. It can allow earlier specialist review, earlier planning, and in some cases earlier recognition of major concerns that might otherwise only become clear later in pregnancy. It is also reasonable to ask your NHS provider exactly what they assess structurally at the 12-week scan, particularly whether they actively look for major abnormalities such as severe heart defects or open spina bifida, as these are among the types of physical conditions formally screened for later in the NHS anomaly pathway.

The short answer is that, under current NHS practice, most severe fetal anomalies (67.3%) are not detected in early pregnancy.

YYou can find the extended analysis of the situation in the UK in this very recent study published in November 2025: Karim et al., Impact of First-Trimester Ultrasound on Early Detection of Major Fetal Anomalies: Nationwide Population-Based Study of Over 1 Million Pregnancies.

This nationwide study should serve as a wake-up call for UK prenatal care. In a population-based analysis of more than 1 million pregnancies across England, only 32.7% of 14 major fetal anomalies were identified before 16 weeks. In other words, around two-thirds had still not been diagnosed by that stage, meaning that for most affected families, important information was delayed until mid-pregnancy or even later.

The study is especially important because 12 of these 14 anomalies are already included in the NHS Fetal Anomaly Screening Programme for the second trimester, at the 20-week scan. This means the problem is not that these conditions are too rare or too obscure to matter; they are major anomalies that the NHS already recognises as important targets for screening. Yet in practice, early detection remains limited and highly variable.

Some of the findings are genuinely alarming. Acrania, one of the commonest, most severe, and most readily recognisable lethal anomalies, was still not identified before 16 weeks in more than 5% of affected pregnancies. For a condition of this severity, any delay in diagnosis matters.

This study is also powerful because it is the first to describe first-trimester anomaly screening practice at population level in England. It included 110 NHS trusts, had an 84% response rate, covered more than 1 million pregnancies, and included every region of the country. These are not isolated observations from a few specialist centres. They are real-world national data showing that the absence of standardised first-trimester structural screening leads to variation, inequity, and delayed diagnosis.

The earliest scan that can give some reassurance about your baby’s heart is a specialist early fetal heart scan, also called an early fetal echocardiogram, at around 12 weeks. In experienced fetal cardiology centres, this scan can detect many major or severe heart defects. Studies in high-risk pregnancies suggest that around 80% of major cardiac abnormalities may be identified at this stage.

However, the baby’s heart is still very small at 12 weeks, so a transabdominal scan may not always provide all the answers. At 11–14 weeks, a transvaginal approach can improve image resolution and may add important detail, especially when combined with the usual transabdominal scan. For this reason, if you are arranging an early fetal heart assessment, it is sensible to ask whether the centre or specialist is experienced in transvaginal early fetal echocardiography before booking.

Transvaginal early fetal echocardiography can be performed in experienced hands up to about 16 weeks, but it still does not replace the standard detailed fetal heart scan later in pregnancy, usually at around 18–22 weeks. A normal scan at 12 weeks cannot exclude all heart problems, particularly more moderate or minor defects, and some abnormalities only become apparent as the heart develops further. Increased nuchal translucency is one of the recognised reasons for offering this extra cardiac assessment.

Because CVS answers only one part of the question. It is excellent for diagnosing or excluding the main chromosomal abnormalities, but it does not assess the baby’s anatomy, it does not diagnose congenital heart defects, and it does not rule out many single-gene conditions that can also present with increased NT. Increased NT is linked not only to chromosomal problems, but also to major structural abnormalities and a wide range of genetic syndromes, even when the CVS result is normal.

This is why additional assessment is often recommended after a normal CVS result. Detailed follow-up ultrasound helps look for structural anomalies that may only become visible later, and fetal echocardiography may be advised because increased NT is associated with a higher risk of congenital heart disease even in chromosomally normal babies.

A further reason is monogenic syndromes. Some conditions, particularly Noonan syndrome and other RASopathies, can be associated with raised NT but will not usually be detected by standard CVS chromosome testing. In selected cases, this is why clinicians may discuss additional genomic testing such as targeted monogenic panels, exome sequencing, or genome sequencing.

R21 is the NHS rapid prenatal exome sequencing pathway in the National Genomic Test Directory. In simple terms, it is a fast genomic test used in ongoing pregnancies when doctors think there may be an underlying single-gene condition and a molecular diagnosis could change pregnancy management. It uses invasive prenatal sampling and is usually requested by a clinical geneticist after multidisciplinary discussion with fetal medicine.

In the setting of increased NT, R21 is not usually the first test for an isolated raised NT. For an isolated NT over 3.5 mm, the usual starting point is chromosomal testing. R21 comes into the picture when the findings suggest a higher chance of a monogenic disorder, particularly if the NT is over 6.5 mm between 11 and 14 weeks and there is at least one additional anomaly, or if there is persistent NT over 3.5 mm together with structural abnormalities in two or more systems. It may also be used in parallel with chromosome testing when increased NT is seen alongside multiple congenital anomalies that would qualify for R21 anyway.

So, in practical terms, R21 is the NHS route to rapid fetal exome testing when increased NT is part of a more complex picture, rather than a stand-alone test for every baby with raised NT. The exact eligibility is determined by the fetal medicine and genetics team, and the criteria can be updated over time.

If you are aware that a standard NHS CVS sample is usually tested only for chromosomal conditions and copy number changes such as microdeletions and microduplications, it is important to understand what this does not exclude. Many genetic syndromes linked with increased NT, including conditions such as Noonan syndrome and Kabuki syndrome, are caused by single-gene changes and would not usually be diagnosed by standard NHS chromosome testing alone. In this situation, some parents wish to consider whole exome sequencing (WES), or in some cases the more comprehensive whole genome sequencing (WGS).

The first step is to ask your NHS Fetal Medicine Unit whether further testing may be possible through the NHS via the R21 rapid prenatal exome sequencing pathway. If the answer is yes, this may allow you to have the test without private cost. NHS rapid prenatal exome results are typically reported in around 3 to 4 weeks, although timings can vary. If your NHS team do not feel that R21 is available in your case, the situation becomes more complicated. The CVS sample is usually held in a regional genetics laboratory or Genomic Laboratory Hub, and if you wish to pursue private testing, arrangements may need to be made for the sample to be released and transferred to a specialist laboratory. This process can be logistically difficult, may involve secure medical courier transfer, and can be expensive.

This is why it is often best to work with a private provider specialising in both fetal ultrasound and genomics, who can coordinate the pathway properly. A very important first step is a private targeted specialist scan, because this may identify structural findings associated with increased NT. If additional abnormalities are found, you may then become eligible for NHS R21 testing and may not need expensive private exome sequencing. If the baby appears structurally normal, the next step is usually detailed counselling with a consultant clinical geneticist, who can explain whether WES or WGS is more appropriate in your situation and help guide the process of sample transfer and further testing. Some private clinics have expertise with this pathway, including London Pregnancy Clinic (LPC), where the process may include a targeted scan, specialist counselling, and support with the practical steps needed if private genomic testing is chosen.