Once considered solely medical waste and routinely discarded as part of the afterbirth, umbilical cord blood (CB) is now commonly used as a source of hematopoietic stem cells (HSCs) for patients in need of HSC transplantation (HSCT)(or, as more commonly referred to, bone marrow transplantation) for the treatment of both malignant and nonmalignant disorders. In fact, more than 20,000 CB transplantations (CBTs) have been performed since the first one in 1988 [1], and this number increases annually as more recent data demonstrate outcomes for CBT recipients paralleling those for conventional HSCT recipients.

Numerous factors make CB a desirable source of HSCs, including ease of procurement and lack of donor attrition, with the ability to process and store the donor cells long term [2]. Importantly, CB donors can be used without the need for a “perfect” HLA match, thereby increasing donor access to HSCT, particularly for minority and mixed ethnicity patients, for whom a suitably matched related or unrelated donor may be difficult to locate. Moreover, despite the greater degree of HLA mismatch, CBT recipients are at decreased risk of developing chronic graft-versus-host disease (GVHD).