What happens to the uterus during the third stage of labor?

During the third stage of labor, the primary role of the uterus is to contract in order to expel the placenta from the body after the delivery of the baby. These contractions are crucial, as they help to detach the placenta from the uterine wall and facilitate its passage through the birth canal. By contracting, the uterus not only ensures that the placenta is expelled efficiently but also minimizes the risk of hemorrhage by constricting blood vessels at the site where the placenta was attached. This process is essential for the mother's recovery post-delivery and for maintaining uterine health.

In contrast to this, the other options illustrate incorrect scenarios during this stage. Expanding the uterus or increasing blood supply does not occur during this phase, and the uterus does not stop contracting; rather, it actively contracts to achieve the expulsion of the placenta. This understanding is vital for grasping the physiological processes involved in labor and the importance of uterine contractions in ensuring a safe delivery and recovery.