The application of a genetic test to the embryos obtained from artificial fertilization before they are implanted in the uterus of the future mother is another biomedical advance that brings significant medical benefits but is also a focus of moral controversy.

Social attitudes towards preimplantation genetic testing depend strongly on the goal being pursued. Some of its main therapeutic indications detection of genetically transmitted diseases and, more recently, the selection of a healthy, compatible embryo that can help cure a brother or sister of a genetic disease deactivate reservations to its use, whereas its possible application in selecting the sex of the future baby activates powerful moral reservations (table 3).

A large majority of citizens are disposed to accept preimplantation genetic diagnosis:

• so a couple with serious genetic diseases can select embryos that do not carry the defective gene (mean scores above 6 points in all cases on a scale from 0 to 10, where 0 means totally unacceptable and 10 totally acceptable)

• so a couple with a child suffering some genetic disease can select embryos that are not affected by the defective gene and conceive a healthy, compatible child that can help cure its brother or sister (mean score likewise exceeding 6 points in almost every country)

• so any couple can detect whether an embryo carries a gene predisposing it to suffer some grave disease in adultho
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