DR SIMON FISHEL When a child is very sick, their quality of life also causes pain and anguish to those who care for that child. When that illness is likely to be terminal, any caring person would do all they could to help. For a parent, this suffering is almost impossible to bear. How much more cruel it is when a child's very survival depends on finding a potential donor who just happens to be a tissue match - meaning that any transfer of tissue, such as stem cells, will not be rejected.

Without such a donor, parents face caring for a very sick child,day and night, to know that,within months or a few years,their child will lose his or her battle for life. It is no surprise that parents will go to any length to avoid this. But is trying to have another baby a "length" too far? Most of the couples I see would wish for another child to continue or complete their family, even while they fear another child could suffer the same affliction. But with today's advances in in vitro fertilisation (IVF), using what is called preimplantation genetic diagnosis (PGD), it is possible to screen out most of these inherited diseases. Imagine choosing an embryo free of disease, which could be selected as a tissue match. What do I mean by an embryo? A few cells (about eight), three days after fertilisation of the egg, at least four days before this tiny ball of cells could even implant in the womb, being 10 times smaller than a full-stop.

Imagine if such an embryo were implanted, and saved the life of its sibling. Many argue that among all the reasons to bring a child into the world, providing it is wanted and loved, this one is as good as any. The fact is, in all the cases with which I have been acquainted to date, this is the reality: these children are wanted and loved as part of the family.

Some argue that it is wrong "deliberately to create" a child for this purpose, butthere are medical and legal systems in place that would examine the interests of all parties and rule on whether tissue donation couldtake place. Refusing to permit such an IVF "saviour sibling" scenario will not prevent this already acceptable medical practice.

Do critics of IVF tissue-matching advocate banning sibling-to-sibling tissue donation? Is this akin to "torture, rape and blackmail", as one senior religious figure was reported to say last week? If so, why has he not spoken out before when these children, who exist after natural conception, have been tissue donors?

The assertion "deliberately creating a child" is emotive hypocrisy, which is still pandered to by some, even within the medical profession. In the real world, where I see many families experiencing great suffering and pain, most medical practitioners advise the parents to consider continuing to have more children (most do want more children anyway) "in the hope that one might per chance be a tissue match".

Unfortunately, the reproductive dice are so stacked against them that they may have severalmore children with the disease, and/or several terminations of pregnancy as a result, or several that are not a tissue match; during which time they have probably watched their child die.

Saviour sibling technology is a healthcare option - the only such option for those sick children and their families when a tissue-matched donor is not available. It helps them achieve their goal more efficiently than can be done by natural conception, which carries many risks.

But we should not forget the cost benefit to society.Each ofthese children, who could be cured, whose family suffering could be ended, actually depend upon medical and social needs costing many millions of pounds of NHS healthcare resources. If they were cured, it would not only be an essential medical achievement, butof considerable social benefit.

Is it not the right, the human right, of any individual to have access to healthcare options? By helping a family deliver a tissue-matched child, we would be doing what that family is trying to achieve through natural means, without risking the appalling consequences. The chance of a child being delivered free of disease and a tissue match is three in 16. We would be helping them bring into the world a very much loved child - all the evidence to datesupports this. Society's existing systems would ensure appropriate procedures would have to be followed before any tissue could be removed from a sibling under the age of consent. In our multicultural, multiethnic society, the needs of one family should be protected as a private matter while causing no damage to others or society at large.

The good brought about by the birth of a tissue-matched sibling far outweighs any perceived harm. Experience with such cases already tells us that most critics' arguments have no bearing on reality, yet because of their personal and dubious moral objections we are in danger of continuing the pain, suffering and death that could be avoided by a novel healthcare option, which also brings with it social benefit. I believe that helping these families by modern medical practices, which occur in a strictly regulated context, is the essence of a 21st-century civilised society. Dr Simon Fishel is managing director of Care Fertility Group.