Presentation: Pregnancy where mother diagnosed with a haemoglobinopathy disease or carrier status confirmed

A pregnant woman attends an antenatal clinic. She is concerned because results from the sickle cell screening test she consented to (as part of her recent antenatal booking appointment) have shown that she is a ‘carrier’ of an atypical haemoglobin or ‘variant’.

• The partner (biological father) should be offered screening when the mother is found to be a carrier of, or is affected by sickle cell disease or thalassaemia, or has had an inconclusive screening result.
  • Testing may be a haematological screen (with a blood film) or a genomic test.
  • Assessing for sickle cell carrier status often does not require genomic testing because it is possible to diagnose using routine haematological investigations.
• If both parents are carriers of genetic variants which cause a significant haemoglobinopathy then prenatal testing should be considered.

• Collect a detailed family, medical and clinical history (if affected with sickle cell disease) from the woman and her partner.
  • In addition, a family origin questionnaire (FOQ), that includes information on the family origins of the woman and the baby’s biological father, should accompany the full blood count (FBC) and haemoglobinopathy screening sample. This enables laboratory clinical scientists to interpret results.
• NHS England has published comprehensive guidelines on when to refer for molecular testing (see the sickle cell and thalassaemia antenatal laboratory handbook). This process is designed to identify couples at risk of severe haemoglobinopathies so that prenatal diagnosis can be performed in a timely fashion.
• Follow local protocols to determine appropriate onward referral. This may be to your local screening team.
• The relevant team will refer to the NHS England National Genomic Test Directory eligibility criteria to determine which tests are available to offer the pregnant woman. The directory itself provides a list of all available tests.
  • For information about how to arrange testing in Wales, Scotland or Northern Ireland, see our dedicated Knowledge Hub resource.
• Genomic testing options depend on the specific variant(s) but may include:
  • Carrier screening for the pregnant woman and the biological father:
    • R361 Haemoglobinopathy trait or carrier testing: For individuals who are likely to have or carry a clinically significant haemoglobinopathy (other than sickle cell disease) based on initial protein testing.
    • R362 Carrier testing for sickle cell disease: For individuals who are likely to carry sickle cell disease, based on initial protein testing or red cell indices.
    • Both the above tests require blood to be collected in an EDTA tube. Refer to your local Genomic Laboratory Hub (GLH) for details of test request forms and where to send samples.
  • Prenatal invasive testing may be offered in pregnancies with a known familial disease-causing variant.
    • Referral to a fetal medicine unit is required
  • Pre-implantation genomic testing (PGT) may be available if the woman presents pre-conceptually. Referral via clinical genetics is required.
• A completed record of discussion form, or an alternative local consent form, will be required by the laboratory to process the sample.
• 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

• NICE: Antenatal care guidelines
• NICE: Sickle cell disease scenario: screening
• NHS England: National Genomic Test Directory
• NHS England: Guidance: Referral of antenatal samples for molecular analysis
• NHS England: Guidance: Sickle cell and thalassaemia screening programme: standards

References:

• Oteng‐Ntim E, Pavord S, Howard R and others. ‘Management of sickle cell disease in pregnancy. A British Society for Haematology Guideline‘. British Journal of Haematology (2021): volume 194, issue 6, pages 980–995. DOI: 10.1111/bjh.17671

For patients

• NHS England: Sickle cell and thalassaemia information
• NHS England: Sickle cell and thalassaemia screening: information for fathers
• NHS England: Maternal medicine networks: service specification
• NHS Health A to Z: Screening for sickle cell and thalassaemia
• Sickle Cell Society: Sickle cell disease information and support
• UK Thalassaemia Society: Thalassaemia information and support