OBJECTIVETo retrospectively study the impacts of ABO incompatibility on early outcome after single unit unrelated cord blood transplantation（UCBT）, such as cumulative incidence of engraftment, incidence of acute graft- versus- host disease （aGVHD） and 180- day transplant- related mortality（TRM）.

METHODS208 patients underwent single unit UCBT from April 2008 to October 2014 were analyzed, included 99 ABO- identical, 60 minor, 38 major and 11 bidirectional ABO- incompatible recipients. All the patients received intensified myeloablative conditioning, and a combination of cyclosporine A and mycophenolate mofetil was given for GVHD prophylaxis.

RESULTSCumulative incidences of neutrophil engraftment, platelet recovery, erythroid lineage reconstitution, Ⅱ-Ⅳ aGVHD, Ⅲ-Ⅳ aGVHD and 180- day TRM showed no significant difference among the patients receiving ABOidentical, minor, major, and bidirectional UCBT（all P>0.05, respectively）. What's more, none of the patients developed pure red- cell aplasia（PRCA）after UCBT. Group A donor and a group O recipient patients didn't appeared to influence the clinical results when compared with others（all P>0.05, respectively）.

CONCLUSIONPatients receive ABO- incompatible UCBT may not develop PRCA. The presence of ABO- incompatibility did not influence the hematopoietic reconstitution, the incidence of aGVHD and 180-day TRM in this cohort. There is not support for the need to regard ABO-compatibility as an UCB-graft selection criterion.