Finding biological markers to assess the ability of embryos to develop is a major objective of research being carried out to improve the results of in vitro fertilization (IVF). Among these markers, the chromosomal content of embryonic cells has been the subject of numerous studies to identify euploid embryos which will be transferred as a priority into the uterus. In France, a clinical research program funded by the Ministry of Health was undertaken to evaluate the benefit of this strategy when IVF is carried out in women aged 35 to 41. This program was interrupted because its authorization was canceled by a court on the grounds that the search for aneuploidy in the embryo is a preimplantation genetic diagnosis (PGD) and that this type of analysis is not provided for in the governing law. The law says in fact that a PGD can only be carried out if “has been previously and precisely identified, in one of the parents or one of their immediate ascendants in the case of a seriously disabling illness, with late revelation and prematurely endangering the vital prognosis”. But the chromosomal analysis provided for in the research protocol is not a diagnosis, it is a test which identifies the embryos most capable of developing. Like all other techniques with the same goal, this test is not the responsibility of the law but of the good practice guide. Studies seeking to improve the results of IVF for the benefit of couples who use it should not be prevented.