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Umbilical cord blood contains hematopoietic stem cells that can be used in bone marrow transplants to treat hematological disorders and blood cancers. There have been over 25,000 transplants done using Umbilical Cord Blood (UCB) and the data from these have indicated that there are less complications when UCB is used; importantly, a reduction in graft rejection and less graft versus host disease.
There are studies demonstrating that using a cord blood unit that is mismatched for one HLA antigen gives equivalent survival rates when compared to using a fully matched bone marrow unit in the treatment of leukemia. This is significant because it is easier for a patient to find a partially matched UCB then a fully matched bone marrow.
Recently, a Japanese study determined that umbilical cord blood is beneficial in the treatment of Myleodysplastic syndromes (MDS). The study notes that the patients with MDS that received a UCB transplant had similar survival rates to those who receieved HLA-mismatched bone marrow transplants.
https://www.mdsbeacon.com/news/2011/10/28/umbilical-cord-blood-transplantation-appears-to-be-a-good-option-for-mds-patients-without-a-matched-bone-marrow-donor/