Umbilical cord is used in place of a bone marrow transplant in the treatment of blood disorders such as leukemia, with donations released for transplant through one registry, Netcord.org, passing 1,000,000 as of January 2013. Cord blood is used when the patient cannot find a matching bone marrow donor; this "extension" of the donor pool has driven the expansion of public banks. The umbilical cord in some mammals, including cows and sheep, contains two distinct umbilical veins. There is only one umbilical vein in the human umbilical cord. In some animals, the mother will gnaw through the cord, thus separating the placenta
Cord blood for and the costs paid by donor families) or public (i.e. stored and made available for use by unrelated donors). While public cord blood banking is widely supported, private cord banking is controversial in both the medical and parenting community. Although umbilical cord blood is well-recognized to be useful for treating hematopoietic and genetic disorders, some controversy surrounds the collection and storage of umbilical cord blood by private banks for the baby's use. Only a small percentage of babies (estimated at between 1 in 1,000 to 1 in 200,000) ever use the umbilical cord blood that is stored. The American