What does it mean to be a good parent, in a situation like the Hashmis'? This may seem an odd question to ask about an exemplary mother and father: after all, are not the Hashmis doing everything they can to save their child? Zain does not, it is true, need saving from imminent death: beta thalassaemia is a chronic, not a terminal condition. However, Zain's health could surely be promoted by a cord blood or bone marrow transplant - including a transplant from a sibling conceived and selected for the purpose.

If all goes to plan, the Hashmis will become the mother and father of this donor child, and of many other human beings. Many embryos will be conceived in vitro on behalf of the Hashmis - perhaps even more than the 30-odd conceived in a past attempt to treat Zain. Almost all these embryos will be destroyed, either because they share Zain's condition or because, though healthy themselves, they would not be suitable donors. To see the Hashmis as good parents to the 30-plus offspring they plan to conceive would be stretching credulity: their attitude to them is more like that of owners or consumers.

What should we say about the survivor, from whom tissue will be taken? This child will know that as many as 60 of his or her siblings have been discarded, as he or she would have been discarded were it not for having features which are useful for Zain. The new child, and Zain himself, will know that they were not accepted unconditionally; rather they are each survivors of a process aimed at screening out certain kinds of offspring. Zain reportedly escaped an abortion only due to an error in prenatal diagnosis; another child was aborted, and the Hashmis have said that they still feel guilt over the abortion. The irony is that they will now embark on a much more profligate expenditure of human lives: both lives affected by beta thalassaemia and those which are not.

It is a clear, if challenging, fact that we all began as human embryos. From the very beginning, we had objective interests (without, of course, taking an interest) in our own human future. This applies as much to the disabled as it does to the able-bodied: life has an intrinsic value, whether one is 'normal' or not. Indeed, the Hashmis recognise this value themselves, at least in the case of Zain; it is because they see Zain's life as precious that they are willing to create and destroy so many lives to promote that of Zain. Human life must, however, be respected first and foremost before it is promoted: only this principle stands between us and wholesale abuse of human rights. Those parents who are seriously tempted to promote life by ending other lives should ask themselves if human rights extend to every human, and children's rights to every child conceived.

Dr Helen Watt is Director of the Linacre Centre for Healthcare Ethics