Postpartum hemorrhage occurring before placental delivery is termed third-stage hemorrhage. Bleeding prior to placental expulsion may not present as sudden massive hemorrhage but rather as steady, controlled bleeding. While the volume at any single point may seem manageable, it persists until severe hypovolemia develops.
Particular attention must be paid to bleeding after placental delivery. The site of placental separation relies on uterine contractions to compress blood vessels and occlude lumens for hemostasis. Uterine atony can lead to immediate and massive blood loss. Delayed hemostasis or blood transfusion may cause the patient to slip into coma or organ failure, posing a life-threatening risk to the mother.
Primary uterine atony refers to the absence of effective contractions from the onset of labor, preventing timely cervical dilation and descent of the presenting part, leading to prolonged labor. Secondary uterine atony occurs when contractions are initially normal but weaken during the later stages of labor (typically late active phase or second stage), causing slowed or arrested progress.