is allowed to dry and separates on its own (typically on the 3rd day after birth), falling off and leaving a healed umbilicus. umbilical cord catheterization as the umbilical vein is directly connected to the central circulation, it can be used as a route for placement of a venous catheter for infusion and medication. the umbilical vein catheter is a reliable alternative to percutaneous peripheral or central venous catheters or intraosseous canulas and may be employed in resuscitation or intensive care of the newborn. blood sampling from 24 to 34 weeks of gestation, when the fetus is typically viable, blood can be taken from the cord in order to test for abnormalities (particularly for hereditary conditions). this diagnostic genetic test procedure is known as percutaneous umbilical cord blood sampling. storage of cord blood main article: cord blood the blood within the umbilical cord, known as cord blood, is a rich and readily available source of primitive, undifferentiated stem cells (of type cd34-positive and cd38-negative). these cord blood cells can be used for bone marrow transplant. some parents choose to have this blood diverted from the baby's umbilical blood transfer through early cord clamping and cutting, to freeze for long-term storage at a cord blood bank should the child ever require the cord blood stem cells (for example, to replace bone marrow destroyed when treating leukemia). this practice is controversial, with critics asserting that early cord blood withdrawal at the time of birth actually increases the likelihood of childhood disease, due to the high volume of blood taken (an average of 108ml) in relation to the baby's total supply (typically 300ml). the royal college of obstetricians and gynaecologists stated in 2006 that "there is still insufficient evidence to recommend directed commercial cord blood collection and stem-cell storage in low-risk families". the american academy of pediatrics has stated that cord blood banking for self-use should be discouraged (as most conditions requiring the use of stem cells will already exist in the cord blood), while banking for general use should be encouraged. in the future, cord blood-derived embryonic-like stem cells (cbes) may be banked and matched with other patients, much like blood and transplanted tissues. the use of cbes could potentially eliminate the ethical difficulties associated with embryonic stem cells (escs). while the american academy of pediatrics discourages private banking except in the case of existing medical need, it also says that information about the potential benefits and limitations of cord blood banking and transplantation should be provided so that parents can make an informed decision. in the united states, cord blood education has been supported by legislators at the federal and state levels. in 2005, the national academy of sciences published an institute of medicine (iom) report which recommended that expectant parents be given a balanced perspective on their options for cord blood banking. in response to their constituents, state legislators across the country are introducing legislation intended to help inform physicians and expectant parents on the options for donating, discarding or banking lifesaving newborn stem cells. currently 17 states, representing two-thirds of u.s. births, have enacted legislation recommended by the iom guidelines. the use of cord blood stem cells in treating conditions such as brain injury and type 1 diabetes is already being studied in humans, and earlier stage research is being conducted for treatments of stroke, and hearing loss. cord blood stored with private banks is typically reserved for use of the donor child only. in contrast, cord blood stored in public banks is accessible to anyone with a closely matching tissue type and demonstrated need. the use of cord blood from public banks is increasing. currently it 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 other animals the umbilical cord in some mammals, including cattle 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 from the offspring. the cord along with the placenta is often eaten by the mother, to provide nourishment and to dispose of tissues that would otherwise attract scavengers or predators. in chimpanzees, the mother leaves the cord in place and nurses her young with the cord and placenta attached until the cord dries out and separates naturally, within a day of birth, at which time the cord is discarded. (this was first documented by zoologists in the wild in 1974.) some species of shark—hammerheads, requiems and smooth-hounds—are viviparous and have an umbilical cord attached to their placenta. animals that lay eggs seem to have a false umbilical-cord that attaches the embryo and yolk together in much the same way. other uses for the term "umbilical cord" the term "umbilical cord" or just "umbilical" has also come to be used for other cords with similar functions, such as the hose connecting surface-supplied divers to their surface supply of air and/or heating, or space-suited astronauts to their spacecraft. engineers sometimes use the term to describe a complex or critical cable connecting a component, especially when composed of bundles of conductors of different colors, thickness and types, terminating in a single multi-contact disconnect. cancer-causing toxicants in human umbilical cords in multiple american and international studies, cancer-causing chemicals have been found in the blood of umbilical cords. these originate from certain plastics, computer circuit boards, fumes and synthetic fragrances among others. over 300 chemical toxicants have been found, including bisphenol a (bpa), tetrabromobisphenol a (tbbpa), teflon-related perfluorooctanoic acid, galaxolide and synthetic musks among others. the studies in america showed higher levels in african americans, hispanic americans and asian americans due, it is thought, to living in areas of higher pollution. additional images sectional plan of the gravid uterus in the third and fourth month. fetus in utero, between fifth and sixth months. a newborn at 45 seconds, with umbilical cord clamped. umbilic. deep dissection. serial cross section. dried umbilical cord stump.