The rules governing 'designer babies' may soon be relaxed to allow more screening and embryo selection.
Dr Mohamed Taranissi of London's Assisted Reproduction Gynaecology Centre is pressing for embryo selection to be allowed for a Northern Ireland couple.
Their son has a rare blood disorder which could be relieved with blood from a sibling's umbilical cord.
The Human Fertilisation and Embryology Authority (HFEA) will review its laws on Wednesday.
However any change in screening rules is likely to prove controversial and be opposed by anti-abortion groups who question the ethics of embryo selection.
What are your views on selecting donor siblings? Are you happy for the law to change?
This debate has now closed. Thank you for your comments.
Never mind the religious aspect of souls etc, we already interfere with nature far too much. We're on a course to our own destruction. What arrogance, thinking that we can interfere with a process which has been successful for thousands of years, and not suffer consequences.
Bridget, Cambridge, England
Astonishing! On the one hand we have laws designed to protect children from exploitation, while on the other we create babies for what we can get out of them. Oh brave new world etc.
Mike Thomas, Swansea
We live in an age where we expect perfect lives. Nature isn't like that and life is richer and more diverse for the variety and for accepting imperfection.
I'm very uncomfortable with the idea of parents having a child specifically to provide tissue to help a sick sibling. Every person who exists is a person in their own right - not a tissue bank for someone else. If adults donate blood, marrow or organs they are able to give consent - a child cannot do this. Having said all that, it seems the case in Northern Ireland will involve taking tissue from the umbilical cord only - not the child itself, so I can't see any real moral or ethical problem with this.
I am very much in two minds over this issue. If a child of mine had a rare blood disorder then I think I would want to do anything to try to save him, but how would the other child feel knowing that he was conceived, not because he was a loved and wanted child, but in order to save a sibling - would that not make him feel second-best?
Linda Callcut, Ely, Cambs, England
Designer babies? Absolutely - everybody's gonna need one for spare parts! Is it only me who finds this a little clinical and bizarre? If you are a family who wants another child, think about how it's going to feel for them: "well we had to engineer you, honey, we didn't want you to come out wrong." Joking aside, one has to consider the impact on the dynamic of a family who is in this position - if the selection process failed (because of the death of the sick child, or the failure of the procedure) what kind of burden will this be for the engineered baby? And to dispel the idea that I'm a religious apologist - I'm an atheist.
Sara George, Fort Worth, USA
My son has cerebral palsy. If my wife and I were told that we could cure him by engineering another baby, which would be impossible, I would not do it. We love him for who he is not who he could be. How do they know that an engineered baby would be perfectly healthy anyway? Why don't they just leave genetic engineering to the realms of Mary Shelley novels?
Ian Simmins, Ottery St Mary, Devon
It's a part of our evolution that drives our way. Everything that we do is not because we want them to be that way. Instead it is the force of nature that shows us our way. We as a part of nature decide which way to go. If using embryo for cure is beneficial then it will be used. Every radically new step taken in science has to bear the initial brunt because of the scepticism in our society.
Ajit Kumar, Mumbai, India
It astounds me how people would be happy to see a child die, or suffer severely, when something could be done to save them. I think I'd be very happy to know I'd helped save my sibling's life when I was born. There would be two lives, one saved, and one created, whereas before there would have been none at all, because the older child might have died, and the younger one would not have been "allowed" to be born.
Shaun Hollingworth, Rotherham, UK
People should also question whether the HFEA should be deciding on this! They are an unelected body and no one on their committee appears to have any qualifications in medical ethics. If the government is making decisions on things like the height of hedges, why on earth are they leaving such an important decision to an unelected quango?
Patrick Leahy, Cambridge, UK
I should welcome any relaxation of the laws. The HFEA is generally very conservative in its approach to these matters compared with most other countries. This has led to a national shortage of egg donors. Many couples end up going abroad as a result of over-restrictive policies here. People have the right to use whatever safe, effective medical procedures are available to help them to have children. The HFEA needs to come into line with other countries.
With the right degree of control absolutely yes! - it is totally illogical to not be able to cure a child when one can. Many fertilised eggs do not "make it" naturally - so for the religious - where is "God" when that happens? Designing a baby for a specific health requirement leads to a much loved first and second child!
Because mankind has been slowly abandoning natural selection (i.e. those with bad genetic mutations are rightly NOT allowed to die) the human race is slowly overloading with unfavourable genes. We either engineer our genes directly or select the best genetic stock (no this has nothing to do with racism or eugenics). Otherwise the average homosapien will in 100,000 years need constant medical attention to stay alive.
Sure, another step along the merry road to a nightmare society where physical perfection is all that matters. We might as well open high street stores where you can browse catalogues, select the characteristics you want and order your baby for delivery, to your home or place of work, on a date and time of your choosing.
John B, UK
I think there is a lot of hypocrisy here (or people who haven't thought this through properly). I can't imagine anyone having a child *only* to help an older sibling - this would surely be an additional reason. Secondly, many, many people have a second child to help their first anyway - they believe that a child is better off not being the only one in the family.
Jane, Lancaster, UK
As the parent of a child who died from a genetic disorder I would not have considered giving birth to another child in the hope of saving the first one. Children should be born because they are wanted and not because their purpose in life has already been decided. Is the ultimate "throwaway commodity" in a throwaway society the human embryos that will be discarded.
Surely if a family was already planning to have a second child then they should be allowed to consider saving their first child in the process?
Please dear God no. I have a great deal of sympathy for the parents but surely this is just a small step towards the floodgates being opened and that will eventually lead us to the divided society that science fiction has feared for years. Has nobody ever watched Gattaca? If nothing else, it seems unethical.
Matt, Canterbury, Kent, UK
If GM food is allowed there is no excuse not to allow 'designer' babies in the full sense.
James St George, London England
Like GM foods, it's all going to happen anyway, regardless of how people feel about it.
Gerry Noble, Salisbury, UK
Where do you draw the line between wanting a baby genetically matched so as to save the life of a sibling and wanting to distinguish between a perfect and slightly imperfect foetus? I don't think humans can ever provide the right answer. We are too swayed by our personal emotions. For suffering families this may seem unfair. I am in a suffering family myself. But life is not about the here and now. We are part of a bigger plan and one day we will understand why there has to be suffering and it won't last for ever.
Please can we ditch all the religious baggage attached to this and acknowledge the reality that if fleas don't have immortal souls then neither do humans? If we are able to grow plants to match our requirements then why not foetuses? Reality means that we eat furry animals for food so please face up can we all grow up and stop living in fairyland.
Sam Martin, Brussels, Belgium
Perhaps the only people that are opposed to this are those who live for their suffering. I believe that if through human engineering we can bring an end to human suffering, we must, we have an obligation to many future lives that have yet to be lived.
It is NOT a question of using technology to help the living - which nobody objects to. The question is what do you do with the human life you bring into being? Do you take the bits you want and dump the rest? Is that a right way to treat a human being, even if he/she is very tiny? You wouldn't take an adult's organs without asking, still less kill an adult to move bits of him/her into someone else.
Phil, UK: The child is not going to be harmed in any way, only a small amount of blood would be taken. Otherwise: If we could use stem cell research to cure cancer, would we accept it? If we could in fact genetically engineer our children to be free from genetic disease, and thus eliminate it from the human species, I would say yes, go for it! The only thing that must not happen is "designer" babies, where people are selected on looks or something - this should happen for the purpose of preventing disease.
Joseph Farthing, UK, EU