Presentation: Fetus with a brain anomaly

A couple attend their anomaly scan at 19 weeks of pregnancy and are told that there is excessive fluid on both sides of their baby’s brain. The baby is diagnosed with moderate ventriculomegaly with a measurement of 14 millimetres. The pregnancy has otherwise been low risk and no associated anomalies can be seen.

• Testing is usually offered in all cases of ventriculomegaly with or without other associated anomalies.
• The chance of identifying an underlying genetic condition increases with more severe ventriculomegaly and where there are associated anomalies.
• It is important that other causes, such as infection, are excluded.

• Refer to local guidance regarding fetal medicine referral. Further review in a fetal medicine unit is usually warranted. A vaginal scan may be undertaken to provide better views of the brain. MRI assessment will be considered.
• Initial genetic referral is not routinely indicated for isolated ventriculomegaly. A fetal medicine review will determine whether genomic testing is appropriate, and referral to clinical genetics will be considered if there are complex issues or multiple anomalies for which a genetic diagnosis is suspected.
• The relevant team will review 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.
  • Where there are multiple or complex anomalies and/or the above testing is non-diagnostic, rapid 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: Ventriculomegaly
• International Society of Ultrasound and Gynaecology (ISUOG): Ventriculomegaly
• NHS England: National Genomic Test Directory
• NHS England: The 20-week screening scan

For patients

• Great Ormond Street Hospital for Children NHS Foundation Trust: Ventriculomegaly
• SHINE: Spina bifida and hydrocephalus information