A new and controversial add-on service for couples undergoing in vitro fertilisation (IVF) is raising profound questions about the future of reproduction. Known as polygenic embryo screening (PES), or polygenic risk scoring, the technique aims to predict an embryo's likelihood of developing common diseases later in life, such as heart disease, diabetes, or certain cancers.
How Does Polygenic Embryo Screening Actually Work?
Unlike traditional genetic screening, which looks for specific, high-risk single-gene mutations like those causing cystic fibrosis, PES evaluates thousands of common genetic variants. Each variant contributes a tiny amount to an overall statistical risk score for complex conditions. In practice, a few cells are taken from a days-old embryo created via IVF. Their DNA is analysed, and a computer algorithm generates a polygenic risk score, estimating the embryo's predisposition to various diseases.
Proponents, including several private clinics, argue this allows prospective parents to select embryos with lower calculated risks. Professor Shai Carmi from the Hebrew University of Jerusalem, whose 2022 study is often cited, suggests that selecting embryos with the most favourable scores could theoretically reduce the risk of some diseases by 20-50% compared to an average embryo. However, this is a population-level statistic with significant limitations for individual cases.
The Scientific and Ethical Minefield
The technology is fraught with scientific caveats and ethical dilemmas. A major issue is that polygenic scores are currently derived from genetic studies conducted almost exclusively on people of European ancestry, making them far less accurate—and potentially misleading—for other ethnic groups. Furthermore, these scores only account for genetic predisposition, ignoring the monumental role of environment, lifestyle, and pure chance in whether a disease develops.
Dr. Karen Temple, a professor of human genetics at the University of Southampton, is a leading UK voice urging caution. She emphasises that the predicted risk reduction is often modest and relative. "You might be moving from a 10% risk to an 8% risk," she explains, questioning whether such a small shift is meaningful for a family. The UK's fertility regulator, the Human Fertilisation and Embryology Authority (HFEA), has given PES a 'red light' in its traffic-light rating system for IVF add-ons, indicating there is no robust evidence it improves live birth rates.
Regulation, Cost, and the 'Designer Baby' Fear
In the UK, PES is not illegal but exists in a regulatory grey area. The HFEA warns clinics that offering it is potentially misleading, as its clinical utility is unproven. Nevertheless, private companies market it directly to consumers, with costs running into thousands of pounds on top of standard IVF fees. This commercialisation raises concerns about creating an unequal access to speculative technology and exploiting the vulnerabilities of couples undergoing stressful fertility treatment.
The spectre of 'designer babies' also looms large. While PES is currently focused on disease risk, the same underlying technology could, in theory, be used to score for traits like height or educational attainment—a prospect that alarms ethicists. The Nuffield Council on Bioethics has called for greater public debate and scrutiny of these technologies. The central question remains: does selecting embryos based on probabilistic health forecasts represent responsible medicine or a problematic step towards a new form of eugenics, driven by consumer choice rather than state mandate?
As the science evolves, so too must the conversation. For now, UK experts agree that robust, long-term studies are desperately needed, and prospective parents should be offered clear, unbiased counselling about the significant limitations and profound implications of polygenic embryo screening.
