'Road map' proposed for extending embryo research limit to 28 days

An international group of experts has proposed a 'road map' suggesting how the longstanding 14-day limit on human embryo research might be extended to 28 days.

Since 1990, UK law has permitted human embryos to be cultured for research purposes until the appearance of an embryonic structure called the primitive streak, or (if the primitive streak has not appeared before that time) for a maximum of 14 days from fertilisation. However, it has become scientifically possible to culture embryos up to this limit, and probably beyond. Doing so could improve our understanding of congenital disorders, placenta development and causes of miscarriage.

'We propose that the research limit be extended to 28 days or complete neural tube closure, whichever occurs first – in a similar way to current 14-day policies,' said an article published in Nature whose authors include PET (Progress Educational Trust) chair of trustees and developmental geneticist Professor Robin Lovell-Badge, from the Francis Crick Institute in London. Other authors of the article include Professor Jacob Hanna from the Weizmann Institute of Science, Rehovot, Israel, and Professor Magdalena Zernicka-Goetz from the California Institute of Technology, both leaders in the field of culturing embryos in vitro.

The article builds upon a Human Fertilisation and Embryology Authority (HFEA) recommendation that the limit be extended to 28 days (see BioNews 1268). The UK government has yet to announce any plans to act upon this recommendation.

The '14-day rule' was proposed in the 1984 Warnock Report, before being incorporated into the Human Fertilisation and Embryology Act 1990. Because the UK was one of the first states to regulate embryo research, it has influenced similar policies globally.

Many understudied developmental stages occur between 14-28 days, including the first stages of spinal and limb development. By 28 days, no neurons have developed, meaning that embryos cannot perceive sensory information or experience pain.

The article in Nature highlights potential ethical issues, including concerns over sentience. 'There's a pressing need to consider how longstanding embryo-research frameworks might be revised in a responsible way,' said the authors. 'We call for a collective effort by scientists, policymakers, ethicists and the wider public to navigate this transition.'

The article discusses strategies for addressing ethical issues and public concerns. Suggestions include pilot projects to build public trust, where select research centres implement the 28-day limit with full ethical review. Additionally, the article argues that all embryo research should be diligently recorded, with checkpoints to allow ethics councils to re-review the limit if embryos develop faster than anticipated.

Separately, a public engagement project has been launched by the Nuffield Council on Bioethics and UK Sciencewise, aiming to provide the UK government with insights into whether and how the limit might be reviewed.

'The 14-day rule has played a crucial role in setting the ethical, social and legal boundaries of human embryo research nationally and internationally. Scientific advances mean the time is right to provide independent advice on arguments relating to any changes to this limit,' said the project's chair Sarah Devaney, professor of healthcare law and regulation at the University of Manchester.