Placental expulsion

[2] As the fetal hypothalamus matures, the activation of the hypothalamic–pituitary–adrenal (HPA) axis initiates labor through two hormonal mechanisms.

ACTH increases fetal cortisol which acts by two mechanisms: PTGS in turn produces prostaglandin E2 which is a catalyst for pregnenolone to C-19 steroids, such as estrogen.

Th1 cells attract an influx of phagocytic leukocytes into the placentome at separation, allowing further degradation of the extracellular matrix.

Active management routinely involves clamping of the umbilical cord, often within seconds or minutes of birth.

Uterine contraction reduces the placental surface area, often forming a temporary hematoma at their former interface.

Premature cord traction can pull the placenta before it has naturally detached from the uterine wall, resulting in hemorrhage.

The review concluded that use of controlled cord traction should be recommended if the care provider has the skills to administer it safely.

A Cochrane database study[4] suggests that blood loss and the risk of postpartum bleeding will be reduced in women offered active management of the third stage of labour.

If the placenta fails to deliver in 30 minutes in a hospital environment, manual extraction may be required if heavy ongoing bleeding occurs.

[8] In most mammalian species, the mother bites through the cord and consumes the placenta, primarily for the benefit of prostaglandin on the uterus after birth.