The third stage of labor begins immediately after the baby is born and concludes with the complete delivery of the placenta and its attached membranes. This final phase is a brief yet concentrated period of risk, often lasting only a few minutes, which is central to the birthing person’s health outcome. The management of this stage is a primary intervention for preventing postpartum hemorrhage, the leading cause of maternal mortality worldwide. Successfully completing this stage ensures the uterus can contract fully, sealing the large blood vessels that supplied the placenta during pregnancy.
The Physiological Process of Placental Delivery
Following the birth of the baby, the uterine muscle fibers, which are now shortened, begin to contract again, causing the internal surface area to decrease. Since the placenta is not elastic, this reduction in the size of its attachment site causes the placenta to shear away from the uterine wall in the spongy layer of the decidua basalis. This separation typically occurs within a few minutes of the baby’s birth, though the entire third stage is considered normal if completed within 30 minutes.
The detachment can happen in one of two ways: the Schultze or Duncan mechanism. Separation that starts centrally, with the fetal side presenting first like an inverted umbrella, is the Schultze mechanism; this typically contains blood loss behind the placenta until expulsion. Conversely, separation that begins at the periphery, leading with the rough maternal side, is the Duncan mechanism, where bleeding may be visible earlier as it escapes past the edges. Providers look for signs that separation has occurred, such as a sudden gush of blood, the lengthening of the umbilical cord, and the uterus rising and becoming firm and globular.
Active Versus Expectant Management Strategies
The process of placental delivery can be guided by two main approaches: active or expectant management. Active Management of the Third Stage of Labor (AMTSL) is a proactive protocol designed to accelerate delivery and minimize blood loss, shown to reduce the risk of severe postpartum hemorrhage. This approach has three components, starting with the prophylactic administration of a uterotonic drug, such as oxytocin, typically given within one minute of the baby’s birth.
The uterotonic medication causes the uterus to contract powerfully, which helps to shear the placenta away and constrict the blood vessels at the placental site. The second component is controlled cord traction, where gentle tension is applied to the umbilical cord while counter-pressure is maintained on the abdomen to support the uterus. The third step involves fundal massage immediately after the placenta is delivered to ensure the uterine muscle remains firm and contracted.
Expectant, or physiological, management involves waiting for the placenta to deliver spontaneously without prophylactic uterotonic drugs or controlled cord traction. This approach relies on the body’s natural processes, often encouraging gravity, pushing efforts, or early suckling/nipple stimulation to promote the release of natural oxytocin. While expectant management is favored for low-risk births, active management is associated with a shorter third stage and a lower average blood loss. Active management reduces the incidence of blood loss greater than 1000 ml and shortens the duration of this stage.
Immediate Post-Placenta Care and Safety Checks
Once the placenta is expelled, immediate safety checks are performed to prevent complications. The medical team inspects the placenta and the attached membranes to ensure they are complete and intact. A retained fragment of placental tissue within the uterus prevents the muscle from contracting fully, which is a major cause of continued bleeding and infection.
A primary focus following delivery is monitoring the tone of the uterus, which must remain firm to compress the open blood vessels at the placental attachment site. Uterine atony, the failure of the uterus to contract adequately, is the most common cause of Postpartum Hemorrhage (PPH). The healthcare provider performs fundal palpation and massage to check for uterine firmness and stimulate contractions if the uterus feels soft or “boggy.”
Continuous monitoring is essential because PPH, defined as a blood loss exceeding 500 ml after a vaginal birth, is the most serious risk following the third stage. By ensuring the uterus is firm and inspecting the placenta for completeness, the medical team addresses the two most common causes of blood loss, allowing for rapid intervention if bleeding persists. Close monitoring of vital signs and maternal well-being continues for at least the first hour postpartum, sometimes referred to as the fourth stage of labor.