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
Umbilical cord also found in a study from 2008. Although there is higher hemoglobin level at 2 months, this effect did not persist beyond 6 months of age. Not clamping the cord for three minutes following the birth of a baby improved outcomes at four years of age. A delay of three minutes or more in umbilical cord clamping after birth reduce the prevalence of anemia in infants. Negative effects of delayed cord clamping include an increased risk of polycythemia. Still, this condition appeared to be benign in studies. Infants whose cord clamping occurred later than 60 seconds after birth had a