Presentation: Fetus with raised nuchal translucency

A couple attend for their first-trimester dating scan. They have elected to have first-trimester screening for trisomy 13, 18 and 21. 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 3.5 millimetres should be offered genomic testing.
• Referral for fetal exome testing can be done in parallel with other genomic tests when the NT is over 6.5 millimetres and another anomaly is present. This can include a minor finding such as:
  • a structural heart anomaly;
  • cystic hygroma;
  • hydrops fetalis; or
  • abdominal wall anomalies.

• 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 available to your patient. The directory itself provides a list of all available tests.
  • For those working within NHS Wales, please consult the All Wales Medical Genomics Service website for information on how to arrange testing.
• For a patient with an enlarged NT, there are several relevant test panels (some will depend on other ultrasound features). They include:
  • R22: QF-PCR for common aneuploidy and chromosomal microarray is standard practice.
  • R21: Fetal exome sequencing can be offered if the phenotype is as described above. An R21 request will process a QF-PCR plus a chromosomal microarray and fetal exome sequencing in parallel. A record of discussion form is required for fetal exome sequencing.
• 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

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

For patients

• Leeds Teaching Hospitals NHS Trust: Increased nuchal translucency measurement: Information for patients