Le diagnostic préimplantatoire appliqué aux maladies génétiques hématologiques avec ou sans typage tissulaire dans le contexte législatif français

Preimplantation genetic diagnosis is based on the analysis of one or two cells (blastomeres) sampled from in vitro fertilized embryos at day-3 to day-5 of development. This procedure is an alternative to conventional prenatal diagnosis for couples at increased risk of transmitting a severe genetic disease. It avoids the risk of pregnancy termination since only healthy embryos are transferred to the maternal uterus. It has been authorized in France since 1999, and today four centres are licensed, in Paris, Strasbourg, Montpellier and Nantes. In the case of haematological diseases or genetic immunodeficiencies, when the affected child is waiting for a bone marrow transplant, the question to add to the diagnosis of the specific genetic condition, a human leukocyte antigen (HLA) typing, comes up. The aim of HLA typing is to identify among the unaffected embryos, the embryo/s that matched the sick child. Such HLA matching is sought for the future child, because once born, he may be a potential donor of cord blood for the affected sibling. However, double-PGD is a very burdensome procedure, with a very low baby-take home rate, and French regulation has further reduced its expected benefits, leading us to stop this program in our centre.