RÉSUMÉ
Conditioning regimen prior to hematopoietic stem cell transplantation have an impact on patient fertility through the use of gonadal irradiation and/or bifunctional alkylating agents. Their impact on fertility depends mainly on the dose used and, in women, on age at the time of treatment. All patients should benefit before treatment from a consultation informing them of the potential impact on fertility and of fertility preservation techniques. In the absence of contraindications, the major toxicity of myeloablative conditioning regimen justifies fertility preservation. There are few data concerning fertility after reduced-intensity conditioning. Despite lower theoretical gonadotoxicity, we also recommend fertility preservation, if possible before transplantation. The fertility preservation techniques used depend on the patient's age, pathology and conditioning. In the event of subsequent use of harvested gonadal tissue in the context of acute leukemia or aggressive lymphoma, it is advisable to assess the risk of reintroduction of tumor cells. Finally, it is recommended to assess gonadal function after transplant, especially after reduced conditioning. If there is persistent residual gonadal function, post-treatment fertility preservation should be discuss.