Presentation: Fetus with ambiguous genitalia

A couple present for their anomaly scan at 21 weeks of pregnancy. The sonographer notices some concerning features in the perineal region when assessing the femur length. The couple are referred to their local fetal medicine unit, where ambiguous genitalia is identified.

• When ambiguous or discordant genitalia is identified on antenatal imaging.
• When there is a confirmed history of a previous pregnancy affected by congenital adrenal hyperplasia (CAH).
• When there is a family history of CAH and/or known carrier status in either parent.

• Collect a detailed family and personal history from the couple.
• Refer the case to clinical genetics for review by a clinical geneticist or genetic counsellor and/or to your local fetal medicine unit, dependant on local protocol.
• The clinical genetics 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.
• Testing options may include:
  • R251 Non-invasive prenatal diagnosis for fetal sexing: Females affected by CAH are at risk of developing virilisation of the genitalia with clitoromegaly. If the fetus is female, consider invasive testing for diagnostic purposes.
  • Invasive testing: may be offered as a primary investigation for diagnostic purposes, or where this is the patient’s preference:
    • R180 Congenital adrenal hyperplasia diagnostic test.
    • For invasive 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.
  • Postnatal testing at birth: genomic testing, electrolytes and urine steroid profile. Monitor for salt-losing crisis until results are available.
• A record of discussion form or other appropriate local consent form is required for testing.
• 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

• Great Ormond Street Hospital for Children NHS Foundation Trust: Congenital adrenal hyperplasia (CAH) information
• National Organization for Rare Disorders: Congenital adrenal hyperplasia information
• NHS England: National Genomic Test Directory and eligibility criteria

For patients

• Great Ormond Street Hospital for Children NHS Foundation Trust: Congenital adrenal hyperplasia (CAH) information (PDF, three pages)
• Great Ormond Street Hospital for Children NHS Foundation Trust: Non-invasive prenatal diagnosis (NIPD) information