Double Unit Cord Blood Transplant in Hematologic Malignancies.

Inclusion Criteria: * Aged 19 and older * Patients scheduled for umbilical cord blood transplantation as a primary allogeneic hematopoietic stem cell transplantation for the treatment of the following hematologic diseases: Acute leukemia (myeloid/lymphoid/mixed lineage) / Myelodysplastic syndromes / Chronic leukemia (myeloid/lymphoid/monocytic) and myeloproliferative neoplasms / Malignant lymphomas, multiple myeloma / Other malignant hematologic malignancies / bone marrow failure diseases, including aplastic anemia \- If all contents of the consent form are understood and consented to in writing. Exclusion Criteria: * Patients with a history of allogeneic hematopoietic stem cell transplantation or those undergoing transplantation for the treatment of engraftment failure (secondary allogeneic hematopoietic stem cell transplantation is an exclusion criterion; however, patients eligible for registration include those undergoing their first allogeneic stem cell transplantation following an autologous stem cell transplantation). * Patients with severe, uncontrolled infections or severe cardiopulmonary dysfunction, as judged by the investigator. * Patients with an ECOG Performance Status (PS) greater than 3 or those receiving mechanical ventilation in the intensive care unit. * Patients who do not consent to participate in the study or those deemed unsuitable for sincere participation by the attending physician.