Expanded Carrier Screening: How Is It Used? What Are the Ethical Implications?

The 2025 Annual Conference of PET (the Progress Educational Trust) was held in central London on 10 December 2025, and was entitled 'What Does Genomics Mean for Fertility Treatment?'. The conference explored the impact of genomics on assisted conception and IVF.

After giving a welcome address, Sarah Norcross – director of PET – chaired the first session, entitled 'Expanded Carrier Screening: How Is It Used? What Are the Ethical Implications?'. The first speaker was Sara Levene, a consultant genetic counsellor and founder of Guided Genetics, whose presentation was entitled 'An Introduction to Recessive Carrier Screening'.

Levene explained that a human has around 20,000 genes (as classically defined) in their genome, and that possibility that mutations can arise in any of these genes. When a person has one copy of an autosomal recessive mutation, they are known as a carrier, typically exhibiting no symptoms and often having no family history of a genetic condition. Everyone has some recessive mutations, but many of these are so rare that the chance of meeting a partner with the same mutation is very small.

Some mutations are more common. For example, among Jewish populations, about one in 25 people is a carrier of Tay Sachs disease. Among people of white European ancestry, a similar proportion of people are carriers of cystic fibrosis.

Carrier screening began with cascade testing, which involves testing members of an affected individual's family. In the NHS, such tests are still only offered where there is a family history of a condition, and carriers' partners are only tested when the relevant gene variant is sufficiently common (at least one in 70) or when a couple is consanguineous.

Expanded carrier screening (ECS) is a more recent offering, usually targeted at people considering parenthood, in which a wider range of recessive mutations are screened regardless of family history. At present, such tests are only available privately.

Levene emphasised that expanded carrier screening tests are not standardised, and that different providers test for different panels of variants or conditions. She also added that such tests can never eliminate risk entirely, as not all genes/variants are screened, and some de novo mutations will not be detected. This was the case in a recently reported incident in which many children were conceived with sperm from a donor carrying a de novo cancer-causing mutation, although in that instance the mutation was not recessive (see BioNews 1291, 1308 and 1319).

That being said, Levene suggested that one of the positive things about ECS is that it might help to normalise carrier status. As people begin to understand that everyone is a carrier of something, associated stigma will hopefully be reduced.

The second speaker – Professor Jackson Kirkman-Brown, science lead at the Birmingham Women's Fertility Centre – discussed ECS in one of the contexts where it is most commonly used, namely egg and sperm donation. In his presentation – entitled 'Gamete Donation and Testing: As Screening Expands, Does the Donor Pool Diminish?' – he asked whether ECS in donor conception helps, impedes or confuses the ultimate goal of assisted conception, namely the birth of a healthy child.

He acknowledged that gametes are a globally traded commodity, and that sperm banks make marketing claims to distinguish their services – 'the only sperm bank that tests for...' – which can then make patients feel as though they need extra tests. However, because ECS is expensive, it either leads to significantly increased treatment costs for recipients of donor gametes or it needs to be amortised over a large number of recipients. The latter results in large numbers of half-siblings, which can lead in turn to other problems (see BioNews 1222, 1240, 1241, 1253, 1278 and 1283).

To illustrate the difficulties of choosing an ideal donor (on the basis of the information available), Professor Kirkman-Brown showed some pictures of actor Daniel Craig playing the role of James Bond. Prospective parents may like the idea of a donor who is as handsome, intelligent and athletic as 007, but the character's less fashionable traits – smoking, heavy drinking and a propensity for violence – may not be included in the donor profile.

Professor Kirkman-Brown also pointed out some additional difficulties. For example, ECS does not look at male age, which is proven to be associated with increased risk. Furthermore, donor profiles seldom list the age of a sperm donor at the time that his sperm was originally donated.

The third presentation was entitled 'Just Because You Can, Doesn't Mean You Should' and was given by Dr Heidi Mertes, chair of Belgium's Federal Commission for Medical and Scientific Research on Embryos In Vitro. Reminding the audience that ECS can never entirely eliminate risk, she quoted the title of the film 'Life as a Fatal Sexually Transmitted Disease', made by the Polish director Krzysztof Zanussi (and named after a statement attributed to the maverick psychiatrist RD Laing).

She outlined two approaches to thinking about ECS. The first approach focuses on preventing inherited disease, which has potential implications for assigning value to different types of lives and how society views disabled people. The second approach focuses on how ECS may support patient autonomy and informed decisionmaking, but may also play into fearmongering and difficulties around risk perception.

Dr Mertes also talked about whether carrier status should be disclosed to patients who are not at risk of having an affected child. Disclosure helps to avoid the need for repeat screening, if patients have future children with other partners, and most patients express a preference to know. At the same time, disclosure can potentially cause anxiety, increase the need for potentially unnecessary family cascade screening, and require more time and resources spent on genetic counselling.

The session's final speaker was Professor Cathy Herbrand, principal investigator at the project Reproduction in the Age of Genomic Medicine: The Emergence, Commercialisation and Implications of PReconception Expanded CArrier Screening (PRECAS). Her presentation – entitled 'Expanded Carrier Screening in the UK: Mind the Policy Gap' – shared results from PRECAS, looking at the adoption of preconception carrier screening in the UK.

She explained that ECS is primarily used in three different contexts, and that there is a lack of consistency between the way it is used these contexts.

• ECS may be offered by private genetics providers, either via a doctor or directly. This route is primarily used by couples planning a family, and is not subject to any specific UK regulation. In this context, there is no requirement to provide access to genetic counselling.
• ECS may be offered by fertility clinics to patients undergoing IVF with their own gametes. This is not subject to any specific UK regulation. The relevant clinics will often enable access to a genetic counsellor.
• ECS may be offered by fertility clinics or donor banks, in the context of gamete donation. Both NHS and private fertility clinics use donor banks that employ ECS, in which case the relevant clinician will receive information about carrier status, and will need to decide what to do. Guidance from the British Fertility Society currently says that clinics should not use sperm from a donor who is a carrier, but if screening panels become sufficiently expansive, this may eventually come to encompass virtually all donors.

Professor Herbrand argued that there is a need for better UK regulation in relation to all three pathways. There is a need for greater consistency, but at the same time, each pathway also needs be considered in its own terms when it comes to developing guidance and best practice standards.

Professor Herbrand explained that the PRECAS project also conducted stakeholder interviews about the usefulness of ECS. Most interviewees felt that ECS should be an option for those who wish to pay for it, and also noted that ECS could protect clinics from liability. However, a small number of interviewees – all of them NHS employees – were not in favour. They cited concerns around inequality and commercialisation, as well as the possibility that carriers will then coming to the NHS for cascade testing, PGT-M and other services, which will in turn increase workloads.

A lively discussion followed these presentations. One audience member asked whether screening could be expanded to encompass later-onset dominant disorders. The speakers agreed that this would entail much more complex genetic counselling, but Dr Mertes added that BRCA2 mutations can already be included in screening panels, because having two copies of the relevant gene variant can cause Fanconi anaemia.

Another audience member pointed out that fertility clinics have widely differing rules, if a selected gamete donor is known to be a carrier. Some clinics require the gamete recipient to undergo full ECS, some just test the recipient for the relevant variant, some mandate genetic counselling, and some have no requirements at all. Levene reminded us that everyone is a carrier of something, and argued that counselling should inform patient choice.

One question concerned whether the advent of ECS signifies a shift in focus, from seeking a healthy baby to seeking a perfect baby. Professor Herbrand agreed that this was a possibility, and argued that it should be made clear that while ECS may reduce certain risks, it cannot eliminate all of them.

Finally, there was a question about so-called 'defensive medicine', in which practitioners anticipate the possibility of a patient having an affected child and then saying: 'There was a test, so why didn't you offer it to me?' Levene said that she had experienced this phenomenon during her own career, and that a balance must be struck, because genetic counsellors do not wish to be in a situation where they could be characterised as pressuring (or 'upselling' to) their patients.

---

PET would like to thank the sponsors of this session (PRECAS) and the other sponsors of its conference (the British Fertility Society, ESHRE, Remaking Fertility, the Adelphi Genetics Forum, the Anne McLaren Memorial Trust Fund, Born Donor Bank, CooperSurgical, Ferring Pharmaceuticals, Merck, Salve, Theramex, Xytex, Juno Genetics and the Institute of Medical Ethics).

Register now for PET's next free-to-attend online events.

• Fertility and the Workplace: Can Employers Help? Should They?, taking place online on Wednesday 14 January 2026 – register here.
• Understanding Egg Donation: The Give and Take, taking place online on Wednesday 28 January 2026 – register here.
• Ancestry, Ethnicity, IVF Outcomes: Why Do Some Patients Fare Better than Others?, taking place online on Wednesday 4 February 2026 – register here.