Final answer:
Maternal blood circulates through the placenta and umbilical cord, exchanging necessary nutrients and gases between mother and fetus until the cord is clamped, leading to the natural occlusion of umbilical blood vessels.
Step-by-step explanation:
During the final stages of childbirth and before the umbilical cord is clamped, maternal blood continues to flow to the placenta. At this stage, the exchange of gases and other substances, such as oxygen and nutrients from mother to fetus and carbon dioxide from fetus to mother, takes place through the umbilical vein and arteries. This physiological process is crucial for the fetus until it is able to breathe on its own and the placenta is expelled from the mother's body. If the umbilical cord is not yet clamped, blood flow between the mother and fetus continues, which is vital for the transition of respiratory and circulatory functions from placental to pulmonary respiration and from fetal to newborn circulation. The clamping and cutting of the cord eventually lead to the natural occlusion of the umbilical blood vessels, marking one of the final steps of the birthing process.