Causes of postpaum hemorrhage include uterine atony, obstetric lacerations, retained placental tissue, and coagulation defects. Atony is the most common cause of postpaum hemorrhage (50% of cases). Predisposing causes include, Excessive manipulation of the uterus General anesthesia (paicularly with halogenated compounds) Uterine overdistension (twins or polyhydramnios) Prolonged labor Grand multiparity Uterine leiomyomas Operative delivery and intrauterine manipulation Oxytocin induction or augmentation of labor Previous hemorrhage in the third stage Uterine infection Extravasation of blood into the myometrium (Couvelaire uterus) Intrinsic myometrial dysfunction Ref: Poggi S.B. (2013). Chapter 21. Postpaum Hemorrhage & the Abnormal Puerperium. In A.H. DeCherney, L. Nathan, N. Laufer, A.S. Roman (Eds), CURRENT Diagnosis & Treatment: Obstetrics & Gynecology, 11e.