Which is the less desirable choice?

16 April 2008

Paul Vallely weighs up the arguments on embryo selection

Should a couple risk having a child, if they know that one of them carries a gene that could give the baby a life-threatening condition, such as cystic fibrosis? Or should they be allowed to screen their embryos, so that only a healthy one is implanted in the mother’s womb? Welcome to another of the moral dilemmas woven into the Human Fertilisation and Embryology Bill, which is currently before Parliament. It is perhaps the central conundrum.

Such screening, known as pre-implantation genetic diagnosis (PGD), can be used only to test for single-gene defects, such as cystic fibrosis. If a family knows that it is at risk, it may opt to use embryo selection, which involves taking several eggs from the mother, fertilising them in a test tube, and then letting the fertilised eggs divide to the eight or 16-cell stage. At this point, a single cell is removed and tested; embryos with the defect are discarded; those that are free of defects are implanted.

The crucial moral dilemma turns on whether the fertilised embryo can be defined as a human person. Conservative moral theology insists that a human person exists once the egg is fertilised by the sperm. But there is another key factor in conception, and that is implantation: until the fertilised egg is implanted in the womb, the fact of fertilisation is insufficient. This is more than saying that the value of any human life depends on its place of residence, uterus or Petri dish; it is to include the necessary consideration of viability. Some 70 per cent of fertilised embryos are thought not to implant in nature; fertilised embryos do not seem to be paramount in the eyes of God.

This is where the space opens between the abortion and the embryology debates. If implantation is a decisive factor, then it does not necessarily follow that the creation of a fertilised egg in vitro is wrong. And, even if the fertilised egg is worthy of respect, it does not follow that it is more worthy of respect than a child or adult with a life-threatening disease.


A dilemma, after all, is a choice between two undesirable alternatives. The destruction of discarded embryos may be a lesser evil than failing to prevent the death of a child or adult.

Unimplanted embryos are clearly human life, but if they are not fully human persons, then PGD may be permissible in certain circumstances. (Legislators should ensure that embryo selection is not permissible for minor disabilities, such as cleft palates.) Although killing a human individual can never be a therapeutic intervention, the gathering of stem cells from an unimplanted embryo might be.

The Vatican’s argument against IVF and embryo selection — and indeed saviour siblings, where a child is born whose umbilical blood can save the life of his or her brother or sister — is that good can never be achieved through the discarding of human beings; even if embryos have defects, they are still persons, and killing them is as wrong as killing disabled people would be. But, if implantation is regarded as a necessary condition, transforming the fertilised egg into the viable embryo, then the argument changes considerably.

There are two alternatives to embryo selection. One is the perfectly legal — but morally much more questionable — option of a late abortion, once the foetus has been tested and shown to carry the life-threatening disease. The other is to condemn such couples to a genetic Russian roulette. Embryo selection seems far less objectionable. It is important in all this that the Church should not confuse the principles of moral theology with the interpretation of scientific fact.

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