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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?

Research with embryonic stem cells (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? It comes down to how the human blastula is viewed.

ESCs are primarily made from cells found in a human blastula, one of the earliest stages of human life. A fertilised egg grows into a blastula (made of ~100 cells), which can only survive for a short time before it must be implanted in a womb. Blastulas used in research are typically made artificially in a laboratory or fertility clinic.

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

Others feel that a blastula is not exactly a child just yet, because unless a blastula is imbedded in the uterus wall, it will never have the chance to develop into a baby.

Every year fertility clinics create many blastula that are destroyed because they are made in surplus. Supporters of ESC research generally feel that using cells from these surplus blastula for research and developing medical treatments, which could help improve and save people?s lives, is much better than throwing them away.

This is where discussion is important. Debates and discussions about the moral and ethical views of 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.

A set of scales

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

In the case of embryonic stem cell research, it is impossible to respect both moral principles.To obtain embryonic stem cells, the early embryo has to be destroyed. This means destroying a potential human life. But embryonic stem cell 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?

Chapter 1 of this film introduces some of the key ethical arguments.
Watch this film and others on our films page.

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 fertilization 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 Arguments against this view

Development from a fertilized 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 will become a person and should be given the respect and dignity of a person.

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 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 for in vitro fertilization 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. A candidate for president is a potential president, but he or she does not have the rights of a president and should not be treated as a president.


2. There is a cut-off point at 14 days after fertilization
Some people argue that a human embryo deserves special protection from around day 14 after fertilization because:

  • 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.
  • 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 brain dead and use them for transplants, then we can also use hundred-cell embryos that have no nervous system.
  • Fertilization is itself a process, not a ‘moment’. An embryo in the earliest stages is not clearly defined as an individual.


3. The embryo has increasing status as it develops
An embryo deserves some protection from the moment the sperm fertilizes the egg, and its moral status increases as it becomes more human-like.

Arguments for this view Arguments against 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 fertilization.
2. Appearance of the primitive streak – the 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 fertilized egg before implantation in the uterus could be granted a lesser degree of respect than a human fetus or a born baby.

More than half of all fertilized 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.

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 still would not say 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 fertilized 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 Arguments against this view

Fertilized 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 it because it has no beliefs, desires, expectations, aims or purposes to be harmed.

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

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 conception and no embryo research should be permitted. Judaism and Islam emphasize 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 embryos. Other religions take other positions.

This factsheet was created by Kristina Hug and reviewed by Göran Hermerén.

Images courtesy of Wellcome Images: Egg and sperm by Spike Walker; Blastocyst on pin by Yorgos Nikas.