Presentation: Fetus with an isolated congenital anomaly

A patient presents at 20 weeks’ gestation for a routine anatomy scan in a low-risk pregnancy. The sonographer detects an apparently isolated congenital anomaly. The remainder of the anatomy scan appears normal. First-trimester screening was low risk and there were no other concerning features.

• Discussion regarding genomic testing is dependent on the anomaly detected. Further details about genomic testing for specific congenital anomalies can be found in other GeNotes articles. See, for example:
  • In the Clinic: A pregnancy at risk of congenital adrenal hyperplasia; and
  • Knowledge Hub: Coarctation of the aorta and Ventriculomegaly.
• Testing should be offered where there is a family history of a genetic condition that is associated with the isolated anomaly seen on the ultrasound.

• Refer to local guidance regarding fetal medicine referral (further review in a fetal medicine unit is usually warranted).
• The fetal medicine review will determine whether genomic testing is appropriate, and referral to clinical genetics will be considered. Referral to clinical genetics is not routinely indicated for a fetal isolated congenital anomaly.
• 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.
• Depending on the clinical scenario, a range of different genomic tests may be considered:
  • Where there is an isolated ventriculomegaly:
    • R22 Fetus with a likely chromosomal abnormality. This will process both:
      • R22.1 Genome-wide common aneuploidy testing; and
      • R22.2 Chromosomal microarray.
    • For certain significant or complex anomalies and/or where above testing is non-diagnostic, fetal exome sequencing may be considered:
      • R21 Fetal anomalies with a likely genetic cause: fetal exome sequencing.
    • Referral to clinical genetics and/or multi-disciplinary discussion is required.
    • A record of discussion form is required.
• For all these tests, an amniocentesis or chorionic villus sample or fetal blood sample (in an EDTA tube) 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: Fetal abnormalities
• National Congenital Anomaly and Rare Disease Registration Service (Public Health England): Congenital anomaly statistics 2018 (PDF, 43 pages)
• NHS England: National Genomic Test Directory
• World Health Organization: Congenital anomalies

For patients

• Please refer patients to the information relating to the specific anomaly detected, which can be found across GeNotes.