Church Teaching
Roman Catholicism
The Roman Catholic Church rejects IVF for several reasons. The main one is that an embryo ought to be treated as a person from the moment of conception, and embryos are discarded in IVF. As a result, Catholicism also rejects PGD when screening for genetic disorders, or PGS when selecting gender. If it became legal to screen for other characteristics, Catholics would reject these procedures on the same grounds.
On top of this, the concept of screening to prevent genetic disorders also suggests that a person with a disorder is somehow inferior, less desirable or not equal. Catholics believe that every person is made by God, in His image, the temple of the Holy Spirit, a unique individual for whom God has a plan etc. In fact, when talking about embryo screening, the Church is quick to draw links with Eugenics, the Nazi attempt to create a master race.
"Interventions which are not directly curative, the purpose of which is 'the production of human beings selected according to sex or other predetermined qualities,' which change the genotype of the individual and of the human species, 'are contrary to the personal dignity of the human being, to his integrity and to his identity. Therefore they can be in no way justified on the pretext that they will produce some beneficial results for humanity in the future,' 'no social or scientific usefulness and no ideological purpose could ever justify an intervention on the human genome unless it be therapeutic, that is its finality must be the natural development of the human being."
More recently, in 2008, in'Dignitas Personae':
Preimplantation diagnosis is a form of prenatal diagnosis connected with techniques of artificial fertilization in which embryos formed in vitro undergo genetic diagnosis before being transferred into a woman's womb. Such diagnosis is done in order to ensure that only embryos free from defects or having the desired sex or other particular qualities are transferred.
...diagnosis before implantation is immediately followed by the elimination of an embryo suspected of having genetic or chromosomal defects, or not having the sex desired, or having other qualities that are not wanted. Preimplantation diagnosis – connected as it is with artificial fertilization, which is itself always intrinsically illicit – is directed toward the qualitative selection and consequent destruction of embryos, which constitutes an act of abortion. Preimplantation diagnosis is therefore the expression of a eugenic mentality that "accepts selective abortion in order to prevent the birth of children affected by various types of anomalies. Such an attitude is shameful and utterly reprehensible, since it presumes to measure the value of a human life only within the parameters of 'normality' and physical well-being, thus opening the way to legitimizing infanticide and euthanasia as well.
By treating the human embryo as mere "laboratory material", the concept itself of human dignity is also subjected to alteration and discrimination. Dignity belongs equally to every single human being, irrespective of his parents' desires, his social condition, educational formation or level of physical development.
Church of England
The Church of England does not share the Roman Catholic view that treats a new life as a human being from conception. This is partly due to the fact that splitting may occur at a later stage (say 2 weeks) so an early embryo cannot yet have a soul. The Church is not as concerned with experimenting on or discarding embryos. However, they are concerned with issues of equality, as well as the idea that screening can treat human life as a commodity (something that is bought and sold).
We would be concerned to see PGD used for anything other than serious genetic disorders, because of the increased commodification of babies. Trivial conditions and non-therapeutic genetic enhancement would not be appropriate reasons for seeking PGD. We also continue to be concerned about purely 'social' justifications of PGD (for example, for family balancing)... Genetics needs to develop for the purpose of therapy, not enhancement.
