Don’t routinely use two cord blood units for standard umbilical cord blood transplantation when a single unit of adequate size is available, recognizing that higher cell doses are preferred when using units with greater HLA mismatch.

Randomized trials demonstrate similar clinical outcomes after single-unit and double-unit umbilical cord blood transplantation, including comparable rates of relapse, engraftment failure, overall survival, and transplantation related mortality. Moreover, graft-versus-host disease may be more frequent after double-cord blood transplantation.

Sources:

Wagner JE, et al. One-unit versus two-unit cord-blood transplantation for hematologic cancers. N Engl J Med. 2014 Oct 30;371(18):1685-94. PMID: 25354103.

Hough R, et al. Recommendations for a standard UK approach to incorporating umbilical cord blood into clinical transplantation practice: an update on cord blood unit selection, donor selection algorithms and conditioning protocols. Br J Haematol. 2016 Feb;172(3):360-70. PMID: 26577457.