脐带
Umbilical cord blood is obtained when a mother donates her infant's umbilical cord and placenta after birth. Cord blood has a higher concentration of HSCs than is normally found in adult blood, but the small quantity of blood obtained from an umbilical cord (typically about 50 ml) makes it more suitable for transplantation into small children than into adults. Newer techniques using "ex vivo" expansion of cord blood units or the use of two cord blood units from different donors allow cord blood transplants to be used in adults.