Buddhism sees a human life as coming after past rebirths in which the individual may have been a human, a heavenly being, an animal, a ghost or a being suffering in a hell. Future rebirths may be of any of such types, depending on the moral quality of a person's actions, their karma. For example, physical cruelty is seen as likely to lead towards a hellish rebirth and generosity and kindness to a human or heavenly one. The working of karma is not about 'rewards' and 'punishments' but a natural process in which a volitional act is like a seed and its karmic results are like fruits. A Buddhist's long-term aim is to overcome the repeated round of countless rebirths, by attaining Nirvana, and to help others do so. Other aims are to bring more happiness to all in this life, and at least gain a good rebirth, as a human or in a heaven.
Rebirth as a human is seen as a relatively rare and precious opportunity for moral and spiritual development - a 'precious human rebirth' - and so to kill a human is definitely worse than killing an animal, although the deliberate killing of any being is against Buddhist ethics. Human life is seen as starting at conception, when the stream of consciousness from a previously deceased being enlivens an egg in the process of being fertilized (whether in a womb or in an IVF test-tube). The question of when the developing embryo 'becomes a person' is not really an issue for Buddhists. An embryo at any stage is alive, conscious and human, though of course its physical and mental faculties take time to fully develop. Consequently, Buddhism sees abortion as morally problematic; a monk who aids an abortion is expelled from the monastic order just as if he had been involved in the murder of a child or adult. Buddhists vary, though, in the extent to which they feel the Buddhist moral view on abortion should be encoded in law. For example, some American Buddhists have argued for an 'anti-abortion/pro-choice' view (1). While, in principle, the age of the embryo does not affect its moral status, in practice one can argue that as the embryo develops, and a relationship with it builds up in the minds of the parents, it becomes more morally perverse to end its life.
How might this perspective inform a Buddhist view of PGD (preimplantation genetic diagnosis)? Here, the basic motivation behind the act is, firstly, to benefit the parents by enabling them to have a child, but not burdening them with an impaired one, and, secondly, not to bring into the world a child suffering from a severe illness. While some may see moral problems with regard to the first goal, due, for example, to concern over an implied slight to those who are disabled, Buddhism sees the main moral issue in relation to the second. Once one has a living embryo one has a very early human being with the genes that it has. Clearly, if one has a group of embryos and one is only going to implant one, or perhaps two, it is better to implant those one knows to be genetically healthier, if one has this knowledge.
Yet this also involves deliberately ending the lives of the remaining embryos - as can also happen in IVF without pre-implantation genetic diagnosis. Given the value of human life, one should only do this in cases of specific, severe genetic illness. It may be that a person born with Down's syndrome goes on to live a life of greater generosity and kindness than someone without the condition and thus makes better spiritual use of their human life. If the embryos are not implanted it should not be done lightly but in acknowledgement that one is ending early human lives with a certain level of consciousness, if not yet consciousness of their environment. Perhaps a simple, voluntary ceremony could mark the event to help the parents deal with their feelings in a clear, conscious and respectful way. Buddhists might also do good deeds on behalf of the deceased embryo(s) so that it might have a chance to mentally participate in the act and benefit karmically.
For Buddhism, it is not simply a question of whether or not to 'create' a being that may have a problematic future. While Buddhism denies that everything that happens is due to karma, who one's new parents are can only be due to karma and it remains highly likely that the specific gene-set one gets from them, including any genetic impairment, is due to karma too. It may be that which sperm and egg successfully fuse to produce a viable embryo is subject to karmic influence: what one might call karmic genetic screening.
However, a severely disabled child, who will suffer extremely poor quality of life or die very young, will need constant care and may place great strain on the parents. In some cases this strain may be intolerable and psychologically and spiritually damaging. It is only, I think, at this point that the morally negative aspects of PGD may be outweighed by the potential spiritual damage that may result from not doing it. One cannot simplistically say that it must be a parent's karma to suffer through having a severely disabled child so they had better just put up with it. They have a choice and that choice needs to be exercised with the utmost care and compassion all round, considering both their own interests and that of any being they will be inviting into their lives.
Alternatives to PGD, which avoid a route involving dead embryos are:
a) to remain childless,
b) to adopt a child,
c) to have a child using a donated sperm via intrauterine insemination (IUI) [where appropriate], or
d) to have a child without knowing whether it will be damaged or not.
Some argue that it is best for a Buddhist not to take the risk, but to accept childlessness or go for adoption. Either way, no-one's short life is deliberately ended and, with adoption, someone is positively helped.