Human embryo research: re-forming societal agreement

The field of human embryology has seen major scientific breakthroughs in the past decade. In 2016, researchers were able to culture human embryos for up to 14 days for the first time, whereas previous techniques could reach only 7 days. And in recent months, scientists have shown that models mimicking human embryo development up to day 14 can be created from stem cells. Although the models are in some ways simplistic, they offer complementary alternatives to using human embryos for research. Such innovations promise to give new insights into the early stages of human development, with the potential to improve health, while raising fresh ethical concerns and testing the limits of current legislation and regulation. How to navigate these benefits and drawbacks is a question for wider society, and the need for an answer is becoming increasingly pressing. Both improved culturing techniques and accurate models of embryo development might help to address important medical needs. Although the success rate of in-vitro fertilisation (IVF) has improved over the past 40 years, about one in three attempts are unsuccessful, often because of implantation failure. A better understanding of the initial developmental processes could lead to improved IVF methods and fewer failures. Likewise, the causes of very early miscarriage are unknown, and risk factors and drivers of many congenital birth defects that are established in early development are not fully understood. Further knowledge of these conditions, and hopefully one day better techniques for management and prevention, could help to bring hope to many millions of families worldwide. However, such developments also stir up anxieties. In particular, regulation appears to be lagging behind the development of embryo models. In the UK, research on cultured human embryos is not permitted past 14 days (and much of the world takes its cue on such matters from the UK), but the models do not appear to fall under this regulation. As the science of these models progresses, the question of whether an embryo model becomes an embryo, and its associated legal status, becomes more urgent. The potential of human embryo culture beyond 14 days is also provoking debate among scientists, ethicists, and philosophers. Because of the 14-day limit, little is known about human gestation between days 14 and 28. But critics fear a slippery slope in which one change in law would make further undesirable and potentially amoral changes far easier. The question of when an embryo becomes an individual is also still open. In 2021, the International Society for Stem Cell Research called for meaningful public engagement to understand how people feel about the 14-day rule. The UK is the first country to respond to this call, by conducting a public dialogue to gauge people's hopes and fears around a potential extension of the 14-day rule. The report of this dialogue, commissioned by the Human Developmental Biology Initiative and UK Research and Innovation Sciencewise, showed that there was overall public support towards some form of extension. Most participants were compelled by the potential benefits for medicine and health. Interestingly, there was a sense of mild surprise and disappointment that the 14-day rule remained unchanged over 30 years, given changes in science and technology. However, there were also strong ethical objections to the development of so-called designer babies. Support for considering changes to the 14-day rule was conditional: research needs continued robust review and oversight, there must be wide and in-depth conversations, and the public cannot be left out of the decision-making process. 40 years ago, no regulatory mechanisms existed for research on human embryos. But the first child born via IVF in 1978, along with other developments in the sciences of embryology and reproductive medicine, generated, like today, both excitement and anxiety. They were the impetus for the establishment of the Committee of Inquiry into Human Fertilisation and Embryology in 1982, led by Baroness Warnock. The committee was tasked with finding a responsible way forward, resulting in the proposal of the 14-day rule and its implementation in the UK Human Fertilisation and Embryology Act 1990. It has served well over the past 30 years, providing a sound basis for carrying out important science responsibly, transparently, and with wider societal consideration and consent. The results have bolstered medicine and safeguarded public trust in research into early human development. Given the recent advances in embryology, and the fresh moral dilemmas that they raise, it now seems time for a fresh inquiry. For more on the culture technique see Nature 2016; 533: 251–54For more on the stem-cell research see Nature 2023; 622: 562–73 For more on the culture technique see Nature 2016; 533: 251–54 For more on the stem-cell research see Nature 2023; 622: 562–73