Presentation: Pregnancy with a paternal history of a rare condition

A couple attend their booking appointment and explain to their midwife that the father has a rare inherited genetic condition. The parents are keen to know whether the pregnancy is affected with the condition so that they can make an informed decision about it and plan for the future.

• Testing should be considered for cases in which the pregnancy is at risk of a serious genetic condition as part of one of two possible scenarios:
  • the condition is autosomal dominant, and the father is either affected or carries a known variant; or
  • the condition is autosomal recessive, and both parents carry different variants.
• Bespoke non-invasive prenatal testing (NIPD) is usually considered for serious conditions that would affect either pre- or postnatal management.

• Collect a detailed family and personal history from the couple.
• Refer to clinical genetics for review by a clinical geneticist or genetic counsellor.
• The clinical genetics team will review the NHS England National Genomic Test Directory eligibility criteria to determine which tests are available to your patients. 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:
  • NIPD: this can be offered for certain conditions in which paternal inheritance is possible. However, a bespoke NIPD test will take a number of weeks to develop. Bespoke NIPD for certain variant types and family histories would fall under R249 NIPD for paternal exclusion testing, for which:
    • the minimum gestation is nine weeks, confirmed by ultrasound scan;
    • 20 millilitres of maternal venous blood in a Streck tube is required; and
    • control samples are required, including paternal and maternal genomic DNA samples (prior carrier status confirmation required).
  • For invasive testing, 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.
• A record of discussion form, or another 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

• NHS England: National Genomic Test Directory
• NHS North Thames Genomic Laboratory Hub (Great Ormond Street Hospital for Children NHS Foundation Trust): Non-invasive prenatal diagnosis