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Embryonic stem cells (ESCs)
Stem cells
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Ethical questions in embryonic stem cell research

Related topics:
Current and Potential Uses Embryonic Stem Cells Ethics and Society

Embryonic stem cells offer hope for new therapies, but their use in research has been hotly debated. Different countries have chosen to regulate embryonic stem cell research in very different ways. Mention embryonic stem cells in the pub and the topic still divides opinion. But what exactly are the ethical arguments, and why are they so tricky to resolve? 

What do we know?

Human embryonic stem cells (ESCs) are created from a small number of cells found in a blastocyst. This is the name for the human embryo at around five days post-fertilisation. A fertilised egg grows into a blastocyst (made of ~100 cells), which can only survive for a short time before it must be implanted in a uterus.  

Blastocysts used in research are typically the result of in vitro fertilisation (IVF). Unfertilised eggs are retrieved, mixed with sperm and cultivated in a laboratory or fertility clinic to reach the blastocyst stage. Cells taken from the blastocyst are then grown under specific conditions in a laboratory to create ESC ‘lines’. (These cell lines are well-studied and understood, and cell lines (rather than cells collected from different individuals) are often used in the lab to reduce the variation in a study.) 

Human ESCs used by most researchers come from these already-existing stem cell lines, rather than new embryos. The ability of ESCs to self-replicate allows huge numbers of cells to be grown from a stem cell line and shared with laboratories around the globe for many years, which minimises the need for making new ESCs from human embryos. 

What are the issues being discussed?

Research with human ESCs is highly debated and many people have strong opinions about it. Both sides of the debate are interested in protecting human life, so why are views so different? 

The debate often centres on how the human blastocyst is viewed. Some people see destroying a blastocyst as ending a human life. 

Another, often overlooked, concern about ESCs is who will and will not benefit from ESC-based treatments. For instance, human ESC-based treatments may not be accessible or affordable for people from disadvantaged economic backgrounds and less wealthy countries. 

The sources of human embryonic stem cells in research

There are two main sources of human ESC lines used in research: 

  1. Cell lines that already exist. 
  2. Spare embryos left over from fertility treatment. 

Embryonic Stem Cell lines

Some people oppose using human ESCs under any circumstances. However, cell lines that already exist are the most widely accepted source of stem cells. This acceptance is based on the argument that “what’s done is done”. Even if harvesting the embryos in the first place could be considered morally controversial, nothing can now be done to save the original embryos from which the lines were created. One could say that there is actually a moral imperative to make the most of existing human ESC lines, for which human embryos were destroyed. 

Using unused embryos from fertility treatments

People who oppose using this source of cells for research are concerned that it shows a lack of respect for the embryos, and therefore for human life. Below is a summary of the arguments for and against using spare embryos. 

Arguments for using unused embryos

  • There is no reason to believe that the destruction of embryos will undermine society’s values – for many years embryos have been created and used for IVF and no significant change has been observed in how we value human life.
  • If it is morally acceptable to use embryos for fertility treatment, where many of them never get implanted into a woman’s uterus and are eventually destroyed, it should not be immoral to use such embryos for curing devastating diseases. (It should be noted that some people object to IVF specifically on the basis that it involves the destruction of unused embros.)
  • The spare embryos will be destroyed anyway, once the time limit for keeping them frozen has expired. It is better not to waste these embryos, but to use them in research that could benefit people. 

Arguments against using unused embryos

If stem cell therapies become routine treatments, then human embryos could be exploited as a source of therapeutic materials, which might indicate a decreasing respect for human life. This is the beginning of a slippery slope, which may lead to dehumanising scenarios like embryo farms or cloned foetuses used for spare parts. This could encourage society to tolerate the loss of life to save a life. Where could that lead?

What are the rationales for differing opinions?

There are over 300 existing human embryonic stem cell lines available in the world. About two-thirds of these are in just five countries: UK, Sweden, France, Spain, USA. 

Some people see destroying a blastocyst for its cells as destroying an unborn child. 

Others feel that a blastocyst is not a child just yet:  unless a blastocyst is embedded in the wall off the uterus, it is impossible for it to develop into a baby.

Every year, fertility clinics create many blastocysts that are destroyed because they are surplus to patient’s family-planning needs. Supporters of human ESC research generally feel that using cells from these surplus blastocysts for research and developing medical treatments, which could help improve and save people's lives, is much better than throwing them away. 

Where does the middle ground lie?

This is where discussion is important. Debates and discussions about the moral and ethical status of human ESCs help establish the rules and regulations that govern scientific research and the development of medical treatments using stem cells. 

It is important to realise that, although people may have very strong opinions on what is "best" for society, groups on both sides of this discussion are interested in helping and protecting human lives. Understanding this can greatly help people to respect each other’s differences in opinions and work to find the middle ground. 

The ethical dilemma

Human embryonic stem cell research poses a moral dilemma. It forces us to choose between two moral principles:  

  • The duty to prevent or alleviate suffering 
  • The duty to respect the value of human life 

Depending on your stance on the status of the early embryo, it may seem impossible for ESC research impossible to respect both moral principles.  

To obtain human ESCs, the early embryo must be destroyed. This means destroying a potential human life. But ESC research could lead to the discovery of new medical treatments that would alleviate the suffering of many people. So which moral principle should have the upper hand in this situation?  

The answer hinges on how we view the embryo. Does it have the status of a person? Is the potential for human life to be granted the same protection as a living person? 

Chapter 1 of this film introduces some of the key ethical arguments.

Conversations: ethics, science, stem cells

The moral status of the embryo

The moral status of the embryo is a controversial and complex issue. The main viewpoints are outlined below. 

1. The embryo has full moral status from fertilisation onwards

Either the embryo is viewed as a person whilst it is still an embryo, or it is seen as a potential person. The criteria for ‘personhood’ are notoriously unclear; different people define what makes a person in different ways.

Arguments for this view

Development from a fertilised egg into to baby is a continuous process and any attempt to pinpoint when personhood begins is arbitrary. A human embryo is a human being in the embryonic stage, just as an infant is a human being in the infant stage. Although an embryo does not currently have the characteristics of a person, it can become a person and should be given the respect and dignity of a person. 

Arguments against this view

An early embryo that has not yet been implanted into the uterus does not have the psychological, emotional or physical properties that we associate with being a person. It therefore does not have any interests to be protected, and we can use it for the benefit of patients (who ARE inarguably persons). 

The embryo cannot develop into a child without being transferred to a woman’s uterus. It needs external help to develop. Even then, the probability that embryos used in IVF will develop into full-term successful births is low. Something that could potentially become a person should not be treated as if it actually were a person.

2. There is a cut-off point at 14 days after fertilisation

Some people argue that a human embryo deserves special protection from around day 14 after fertilisation because: 

  • Before day 14, the embryo has no central nervous system and therefore no senses. If we can take organs from patients who have been declared to have no brain activity and use them for transplants, then we can also use hundred-cell embryos that have no nervous system. 
  • Fertilisation is itself a process, not a ‘moment’. An embryo in the earliest stages is not clearly defined as an individual. 
  • After 14 days the embryo can no longer split to form twins. Before this point, the embryo could still be split to become two or more babies, or it might fail to develop at all. 

3. The embryo has increasing status as it develops 

An embryo deserves some protection from the moment the sperm fertilises the egg, and its moral status increases as it becomes more human-like. 

Arguments for this view 

  • There are several stages of development that could be given increasing moral status: 

1. Implantation of the embryo into the uterus wall around six days after fertilisation. 
 
2. Appearance of the primitive streak – the early beginnings of the nervous system – at around 14 days. 
 
3. The phase when the baby could survive if born prematurely. 
 
4. Birth.  

  • If a life is lost, we tend to feel differently about it depending on the stage of the lost life. A fertilised egg before implantation in the uterus could be granted a lesser degree of respect than a human foetus or a born baby.  
  • More than half of all fertilised eggs are lost due to natural causes. If the natural process involves such loss, then using some embryos in stem cell research should not worry us either. 

Arguments against this view

  • We protect a person’s life and interests not because they are valuable from the point of view of the universe, but because they are important to the person concerned. Whatever moral status the human embryo has for us, the life that it lives has a value to the embryo itself. 
  • If we judge the moral status of the embryo from its age, then we are making arbitrary decisions about who is human.  For example, even if we say formation of the nervous system marks the start of personhood, we would not say that a patient who has lost nerve cells in a stroke has become less human. (But there is a difference between losing some nerve cells and losing the complete nervous system - or never having had a nervous system). 

  • If we are not sure whether a fertilised egg should be considered a human being, then we should not destroy it. A hunter does not shoot if he is not sure whether his target is a deer or a man. 

4. The embryo has no moral status at all

 

An embryo is organic material with a status no different from other body parts. 

Arguments for this view

  • Fertilised human eggs are just parts of other people’s bodies until they have developed enough to survive independently. The only respect due to blastocysts is the respect that should be shown to other people’s property.
  • If we destroy a blastocyst before implantation into the uterus, we do not harm the blastocyst itself, because it has no beliefs, desires, expectations, aims or purposes to be harmed. 

Arguments against this view

  • By taking embryonic cells out of an early embryo, we prevent the embryo from developing in its normal way. This means that it is prevented from becoming what it was programmed to become – a human being. 

Embryonic Stem Cells and religion

Different religions view the status of the early human embryo in different ways. For example, the Roman Catholic, Orthodox and conservative Protestant Churches believe the embryo has the status of a human from the moment of conception and no embryo research should be permitted. Judaism and Islam emphasise the importance of helping others and argue that the embryo does not have full human status before 40 days, so both these religions permit some research on human embryos. Other religions take a range of positions on the issue.

Other issues

The source of human ESCs, and the moral status of the cells used, is not the only ethical issue to consider. It is uncertain who will benefit from stem-cell-based therapies. However, it seems unlikely that the poorer countries in the world will reap the rewards, at least to begin with. Many other ethical questions are raised by the prospect of new therapies, and by discoveries such as induced pluripotent stem cells.

Find out more

Acknowledgements and Copyright

This factsheet was created by Kristina Hug. 

Reviewed in 2011 by Göran Hermerén. 

Reviewed and edited in 2018 by Göran Hermerén. 

Reviewed and updated in 2024 by Prof. Ivana Barbaric, Professor of Stem Cell Biology, and Dr. Rebecca Lea, Centre for Stem Cell Biology, School of Biosciences, The University of Sheffield.

Images courtesy of Wellcome Images: Blastocyst on pin by Yorgos Nikas. 

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