A cord blood unit is the term used for the blood collected from the umbilical cord and placenta after a baby is born. Cord blood is rich in blood-forming cells known as “Stem Cells” that can be used in transplants for patients with leukemia, lymphoma and many other life-threatening diseases. Cord blood is one of three sources of cells used in transplant; the other two are bone marrow and peripheral (circulating) blood (also called peripheral blood stem cell or PBSC transplants).