UK Code of Practice for Stem Cell-Based Embryo Models
Author: University of Cambridge
Published: 4 Jul 2024 - Updated: 4 Nov 2026
Publication Type: Reports & Proceedings
Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content
Synopsis
This report describes the Code of Practice for the Generation and Use of Human Stem Cell-Based Embryo Models, released in July 2024 as the first UK framework for research on lab-grown structures that mimic early human development. It was led by Cambridge Reproduction at the University of Cambridge with the Progress Educational Trust, drawing on scientists, lawyers, ethicists, regulators and a public dialogue. Key points include review of every project by a dedicated oversight committee, justification of how long each model is grown instead of one fixed limit, and an absolute ban on transferring a model into a human or animal womb. The code matters because embryo models could improve understanding of miscarriage, birth defects and IVF failure, research that bears on many families and people with congenital conditions, while giving the public assurance that the work is closely watched.*
At a Glance
- 1 - The code is voluntary and is not law.
- 2 - It will be reviewed regularly as the science develops.
- 3 - Embryo models are meant to complement, not replace, research on donated human embryos.
- 4 - Funders and journals are urged to refuse support or publication for work that does not meet the code.
Topic Definition
- Stem Cell-Based Embryo Model
A stem cell-based embryo model (SCBEM) is a three-dimensional structure grown in the laboratory from stem cells that copies some features of an early human embryo, such as its first cell layers or the tissues that would form the placenta. Embryo models are not made by fertilization and are not considered embryos, but they allow scientists to study stages of early development, pregnancy loss and congenital conditions that are otherwise very hard to observe.
Overview
Stem cell-based embryo models (SCBEMs) are three-dimensional biological structures that mimic aspects of early human embryo development. They can be created in the lab from stem cells, and can provide new insights into critical stages of early human development that are normally inaccessible to researchers.
Embryo model work is expected to lead to new interventions for a range of conditions, including revolutionizing treatments for recurrent miscarriage, understanding developmental disorders and improving the success rate of IVF.
Although embryo models are not the same as human embryos, they mimic aspects of early human development - and this has raised ethical concerns.
The previous lack of a regulatory framework for the use of SCBEMs in research has left scientists and research organizations uncertain about the acceptable boundaries of their work, both legally and ethically, and unsupported in their decision-making. Signing up to the SCBEM Code of Practice will remove these obstacles.
The guidelines, released in July 2024, provide the first code of practice for the use of stem cell-based embryo models in the UK.
"The new Code of Practice provides processes for decision-making in research using stem cell-based embryo models so that scientists can proceed confidently, while maintaining public trust in this vital area of research," said Kathy Niakan, Chair of Cambridge Reproduction and Professor of Reproductive Physiology at the University of Cambridge, and member of the SCBEM Code of Practice Working Group.
"We are confident that the Code will enable the UK to continue to lead the world in research into early human development, while ensuring that this research is ethically robust," said Professor Roger Sturmey, Professor of Reproductive Medicine at Hull York Medical School and Chair of the SCBEM Code of Practice Working Group.
Key Points of the Code
The new SCBEM Code of Practice sets out standards to make sure that research using SCBEMs is rigorous, upholds ethical principles and maximizes the potential benefits. Key to this will be a dedicated Oversight Committee that will review each proposed research project.
The Code recognizes that there must be a limit to how long embryo models can be grown in the lab. However, many different types of embryo model are being developed, representing distinct developmental stages and developing at different rates, making it impossible to impose a single fixed limit. Instead, researchers are asked to provide clear justification of the length of their experiments on a case-by-case basis.
The Code prohibits any human SCBEM from being transferred into the womb of a human or animal, or being allowed to develop into a viable organism in the lab.
"Embryo models have huge potential and we want to realize this, while also limiting the risks. The new Code of Practice will allow stem cell-based embryo models to be grown in the lab long enough to gain meaningful biological understanding, but the Code asks researchers to fully justify what they're doing in scientific and ethical terms," said Niakan.
How Are Embryo Models Useful to Research?
Research using embryo models can improve knowledge of human development, including early pregnancy loss and pregnancy disorders, congenital defects and the precursor events that affect adult human health and disease.
The models could also be used for some investigations that are not permitted using human embryos. For example, there are currently significant limitations to clinical trials and the use of many medicines during pregnancy. Models of early development could be helpful to improve options for drug treatments during pregnancy in the future.
Stem cell-based embryo models open new research avenues that can complement, but not replace, the limited studies possible with actual human embryos. The SCBEM Code of Practice states that neither of these areas of research can or should replace the other for the foreseeable future.
How Was the Code Produced?
The SCBEM Code of Practice Working Group was made up of researchers and practitioners at institutions across the UK, including experts in science, law, ethics and regulation. In drawing up the Code, the team consulted widely with researchers, practitioners, and major funders and regulators of embryo model research, both within the UK and internationally.
The SCBEM Code of Practice Working Group included researchers and practitioners from the Babraham Institute, Biolawgy, Brighton and Sussex Medical School, the Centre of Medical Law and Ethics at King's College London, the Francis Crick Institute, Hull York Medical School, the Medical Research Council, Newcastle University, University College London, the University of Cambridge, the University of Edinburgh, the University of Exeter and the University of Manchester.
The work was also informed by a public dialogue, held earlier in 2024, to explore public attitudes towards research involving embryo models.
"Throughout the process of developing the Code of Practice, we've been keen to engage with as wide a range of stakeholders as possible, including researchers, experts in law and bioethics, regulators and funders," said Christina Rozeik, Program Manager of Cambridge Reproduction and member of the SCBEM Code of Practice Project Team.
She added:
"A public dialogue enabled us to include public voices during the development of the Code, taking account of their hopes, concerns and sensitivities around research involving stem cell-based embryo models. Participants were excited by the potential of embryo model research, but also strongly supportive of oversight."
"Research involving stem cell-based embryo models has enormous potential to improve human knowledge and health, but clearer governance is needed to help researchers work responsibly and maintain public trust. Our Code of Practice addresses this need. It takes into account an extensive range of expert and lay perspectives we've gathered over the past year," said Sandy Starr, Deputy Director of the Progress Educational Trust (PET) and member of the SCBEM Code of Practice Project Team.
How Will the Code Be Enforced?
The Code is not legislative, but the team proposes that it should be adopted by UK researchers, funders, research organizations, professional societies and publishers.
Widespread use is expected to set a new precedent for reporting research utilizing stem cell-based embryo models and deter the funding and publication of research that fails to meet the standards set out in the Code. As a result, adherence to the Code will become an essential part of credible science, providing increased transparency and accountability for embryo model research.
Given the rapid pace of research using embryo models, the Code will be reviewed regularly.
"Research using stem cell-based embryo models is very new, and our understanding of the science is rapidly evolving. We've taken the opportunity to respond to the current situation, and we'll continue to update the Code of Practice as the science continues to develop," said Niakan.
"Establishing this guidance takes stem cell-based embryo models out of the gray zone and onto more stable footing so we can fully explore their usefulness, while providing the essential reassurance that this research is being conducted carefully and with appropriate scrutiny," said Dr Peter Rugg-Gunn, Group Leader and Head of Public Engagement at the Babraham Institute, and member of the SCBEM Code of Practice Working Group.
Creation of the SCBEM Code of Practice (fully titled: Code of Practice for the Generation and Use of Human Stem Cell-Based Embryo Models) was led by Cambridge Reproduction - an interdisciplinary research center at the University of Cambridge - in partnership with the Progress Educational Trust (PET) - a charity that improves choices for people affected by infertility and genetic conditions.
Related Information
- Adult Stem Cells Convert into Embryonic-like Stem Cells: Neural stem cells can take on the characteristics of embryonic stem cells with the addition of a single transcription factor.
- Embryonic Stem Cell Trials Approved by FDA: The Food and Drug Administration has approved the use of embryonic stem cells in human trials for the first time.
- New Guidelines for Stem Cell Research: The stem cell controversy has ruffled the Congress State Legislatures President Bush and the whole of the United Nations.
- UCSF Closer to Creating Safe Embryonic like Stem Cells: Embryonic stem cells have the capacity to become any cell type in the body.
- China Leads the Way in Regenerative Stem Cell Therapy Despite Skepticism: China becoming world leader in stem cell therapy and regenerative medicine despite world skepticism of stem cell therapies.
- Action to Reverse Judicial Embryonic Stem Cell Research Ban: Congressman CSHL president urge quick action to reverse judicial embryonic stem cell research ban.
- Research!America Asks Congress to Support Embryonic Stem Cell Research: Call on Congress to take legislative action that will allow federal funding for human embryonic stem cell research to proceed.
Frequently Asked Questions
NOTE: Researched FAQs by Disabled World (DW)
Can an embryo model develop into a baby?
No, current embryo models lack parts needed for full development, and the UK code forbids transferring them to a womb or growing them into a viable organism.
How are embryo models different from IVF embryos?
IVF embryos come from an egg fertilized by sperm and can lead to a pregnancy if transferred. Embryo models are built from stem cells and only mimic certain features of early development.
What is the 14-day rule?
The 14-day rule limits research on human embryos to the first 14 days after fertilization, around when the primitive streak appears. In the UK it is set in law for embryos, but it does not directly cover stem cell-based models.
Where do the stem cells used in embryo models come from?
They can come from embryonic stem cell lines or from adult cells reprogrammed into induced pluripotent stem cells. Each source has its own consent and ethics requirements.
Who oversees embryo research in the UK?
Research on human embryos is licensed by the national fertility regulator, the HFEA. Embryo models fall outside that law, which is why the voluntary code and its oversight committee were created.
Could embryo model research help prevent miscarriage?
It may in time, because the models allow scientists to study the earliest stages of pregnancy where many losses happen. Any treatments would still need years of further research and clinical trials.
Do other countries have rules for embryo models?
Rules vary widely, and many countries have no specific law yet. The International Society for Stem Cell Research also publishes guidelines that cover embryo models.
Why do people with disabilities follow embryo research?
Some hope it will explain the causes of congenital conditions and improve care, while others raise concerns about how such knowledge could be used in prenatal screening. Both views shape the public debate.
Insights, Analysis, and Developments
Editorial Note: Embryo models sit in a legal gap in the UK because the national embryo research law was written for embryos made from eggs and sperm, not for structures grown from stem cells. The new code fills that gap with self-regulation backed by funders and publishers, an approach that can move faster than legislation but depends on broad buy-in. For people living with genetic or developmental conditions, the research could eventually explain why some pregnancies fail or why certain birth defects arise at stages that have been impossible to observe. Readers following the issue should watch whether regulators move toward formal rules, since a voluntary code is only as strong as the institutions that agree to follow it.*
Attribution/Source(s): This quality-reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally issued as a press release by University of Cambridge and published on 4 Jul 2024. Last updated on 4 Nov 2026. This content may have been edited for style, clarity, or brevity.
* Editorial additions by Ian C. Langtree.