[Genetic diagnosis of the embryo before implantation]

The association of recent progress in two initially faraway fields, assisted reproductive technology and molecular biology, has made way for the preimplantation genetic diagnosis (PGD). For some people this new technique was, immediately, considered as an alternative to prenatal diagnosis for couples at risk of offspring affected with severe genetic diseases. This technique has the advantage of avoiding an eventual abortion and replacing it by an in vitro embryos preselection. For others PGD appeared, above all, as matter of new eugenic risk. In fact, these excessive hopes and fears have contributed to blurring the true current problems of PGD, technical difficulties and still limited reliability. While the French law has admitted the principle of PGD use, the measures for its application remain to be defined. But this legal authorization must recognize that this new technique will be, for a long time, at the stage of research, improvement and assessment.