Presentation: Fetus with raised nuchal translucency

A couple attend their first-trimester dating scan. They have elected to have first-trimester screening for trisomies 21, 18 and 13. During their scan, they are told that the fetus has an increased nuchal translucency (NT) measurement. They have a follow-up consultation with the screening team to discuss their options, and proceed with an appointment with the fetal medicine team.

• Any pregnancy with an NT over 3.5mm should be offered genomic testing.
• Referral for fetal exome testing can be considered in parallel with other genomic tests when the NT is over 6.5mm and another anomaly is present. This can include a minor finding.

• Refer to local guidance regarding fetal medicine referral.
• Referral to clinical genetics is not routinely indicated for an isolated raised NT. The fetal medicine review will determine whether genomic testing is appropriate, and referral to clinical genetics can be considered in certain circumstances.
• The relevant team will refer to the NHS England National Genomic Test Directory eligibility criteria to determine which tests are relevant.
• • For information about how to arrange testing in Wales, Scotland or Northern Ireland, see our dedicated Knowledge Hub resource.
• For a pregnancy with an enlarged NT, there are several relevant test panels (some will depend on other ultrasound features). They include the below.
• • Where there is an isolated anomaly:
• • • R22 Fetus with a likely chromosomal abnormality. Unless clinical information and/or initial results indicate otherwise, R22 requests will process both:
• • • • R22.1 Genome-wide common aneuploidy testing; and
• • • • R22.2 Genome-wide microarray.
• • Where there are multiple or complex anomalies:
• • • R21 Fetal anomalies with a likely genetic cause. Fetal exome sequencing can be offered if the phenotype is as described above. Unless clinical information and/or initial results indicate otherwise, R21 requests will process:
• • • • R21.1 Genome-wide common aneuploidy testing;
• • • • R21.2 Fetal anomalies whole exome sequencing or large panel sequencing; and
• • • • R21.3 Genome-wide microarray.
• • • • A record of discussion form is required for fetal exome sequencing.
• • • • Note that a normal chromosomal microarray is a prerequisite for R21 testing for this indication.
• For DNA-based tests (all the above listed tests), an EDTA sample is required. For many of the tests (particularly whole genome and exome sequencing), parental samples are also needed or are helpful. Please refer to your local Genomic Laboratory Hub for details of test request forms and where to send samples.
• Information about patient eligibility and test indications was correct at the time of writing. When requesting a test, please refer to the National Genomic Test Directory to confirm the right test for your patient.

For clinicians

• NHS England: National Genomic Test Directory
• The Fetal Medicine Foundation: Nuchal translucency at 11–13 weeks of pregnancy (video, two minutes)

For patients

• Liverpool Women’s NHS Foundation Trust: When a Scan Shows a Nuchal Translucency (NT) Measurement of 3.5 Millimetres or More – Information Leaflet (PDF, two pages)