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
Percutaneous umbilical cord blood sampling are self-resolved within five minutes. The complication of infection has a low incidence rate, and preventative measures are implemented against the risk of infection, such as antibiotic usage and the aseptic technique. However, vertical transmission of a virus such as HIV may occur. Fetal loss may also occur, especially in the presence of several risk factors, including fetal abnormalities, operator errors, placental penetration, and viability of the fetus. Intrahepatic vein fetal blood sampling may be done as an alternative to PUBS. It involves the needle being inserted into the intrahepatic part of the umbilical cord in the fetal abdomen. The