Umbilical cord blood is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is obtained from the umbilical cord at the time of childbirth, after the cord has been detached from the newborn. Cord blood is collected because it contains stem cells, including hematopoietic cells, which can be used to treat hematopoietic and genetic disorders. Some placental blood may be returned to the neonatal circulation if the umbilical cord is not prematurely clamped. In some obstetric and midwifery practices, physiological extended-delayed cord clamping protocol, as well as water birth, allows for the cord blood to pulse into the neonate for 2–20 minutes after delivery. If the umbilical cord is not clamped, a physiological clamping occurs upon interaction with cold air, when the internal gelatinous substance, called Wharton’s jelly, swells around the umbilical artery and veins.