Final answer:
The placenta normally separates and is delivered during the afterbirth stage, which can last from a few minutes to about half an hour. The myometrium contracts to aid this process, and if the placenta is not delivered within 30 minutes, medical assistance may be required.
Step-by-step explanation:
Normally, during the afterbirth stage, the placenta separates and is delivered. This process can take anywhere from a few minutes to half an hour after the newborn has been expelled. As the last stage in childbirth, the myometrium—the muscular layer of the uterine wall—continues to contract. This helps shear the placenta from the back of the uterine wall, making it possible for it to pass through the vagina.
After the delivery of the placenta, uterine contractions help minimize blood loss at the site where the placenta was attached. This delivery also signifies the beginning of the postpartum period, a time when the mother's body readjusts to a non-pregnant state over the course of about six weeks. If the placenta does not spontaneously separate and is not delivered within approximately 30 minutes, medical intervention may be necessary to avoid potential complications like postpartum hemorrhage.