Prenatal Genetics Service at the Department of Clinical Genetics at University Hospital Bristol and Weston

In most cases, prenatal development occurs normally and follows the established patterns of development with little variation. However, several things, usually caused by genetics or environmental problems, can go wrong during this time. It has been estimated that approximately 2–4% of pregnancies are complicated by significant problems in the fetus. In some cases, these can be caused by genetic problems that impact both the current and future growth of the developing baby in the womb. In these situations, counselling is offered, including review of options for genetic testing.

The Department of Clinical Genetics at University Hospital Bristol and Weston (UHBW) provides specialist adult and paediatric genetic in our region (Avon, Somerset, Gloucester & West Wiltshire). Besides from our elective clinics and ward reviews, we manage urgent referrals, including prenatal and foetal medicine situations, facilitating genetic counselling and diagnosis, and enabling the interpretation of genetic test results.

Our prenatal work focuses on women and couples with a family history of a genetic condition, or for those with abnormalities presenting during a pregnancy. The team at UHBW works closely with patients alongside our local midwives and Fetal Medicine Units. Prenatal genetic counselling and testing is often indicated for carrier screening for couples, who have a high risk of passing down certain inherited genetic conditions, such as cystic fibrosis or spinal muscular atrophy. In some cases, genetic testing can help pinpoint the cause of repeated miscarriages that could help guide future options for conceiving such as in vitro fertilization (IVF) combined with preimplantation genetic screening.

In cases of abnormalities presenting during a pregnancy, the prenatal testing strategy and test selection should be individualized and guided by prenatal imaging findings and family history. Current options include chromosomal studies by qPCR and chromosomal microarray analysis, with consideration of targeted gene-specific molecular testing for suspected disorders and/or whole genome sequencing (R21). A genetic diagnosis can assist in determining the fetal prognosis and inform prenatal care, including decisions about continuation of pregnancy, delivery planning, and neonatal management, potentially decreasing morbidity and mortality. It may also refine the recurrence risk

leading to informed genetic counselling where future reproductive options, including preimplantation genetic testing, diagnostic prenatal testing, or consideration of donor gametes could be addressed.

Prenatal enquiries and referrals can be directed to: ubh-tr.ClinicalGeneticsUHB@nhs.net

Patients from Devon, Cornwall and the Isles of Scilly, should be referred to the Peninsula Clinical Genetics, hosted by the Royal Devon University Healthcare NHS Foundation Trust (https://www.royaldevon.nhs.uk/services/genetics-and-genomics/peninsula-clinical-genetics/ ).

Patients from Wales should be referred to the All Wales Medical Genomics Service (https://medicalgenomicswales.co.uk/).

Given the urgent nature of the prenatal setting, referrals by post are strongly discouraged.

Further information can be found in these sites:

1. Our website https://www.uhbristol.nhs.uk/pati

ents-and-visitors/your-hospitals/st-michaels-hospital/what-we-do/clinical-genetics/

2. Prenatal genomics – an overview, by Health Education England https://www.genomicseducation.hee.nhs.uk/blog/prenatal-genomics-an-overview/

3. R21: Rapid prenatal exome sequencing https://www.genomicseducation.hee.nhs.uk/genotes/knowledge-hub/r21-rapid-prenatal-exome-sequencing/

4. Screening tests in pregnancy, on the NHS website https://www.nhs.uk/pregnancy/your-pregnancy-care/screening-tests/

5. Ethical issues in prenatal genetic diagnosis, by the Royal College of Physicians https://www.rcplondon.ac.uk/projects/outputs/ethical-issues-prenatal-genetic-diagnosishttps://www.genomicseducation.hee.nhs.uk/blog/prenatal-genomics-an-overview/