Which among the following is the commonest cause of postpaum haemorrhage?

Postpaum hemorrhage refers to excessive bleeding more than 500 ml following delivery. Uterine atony is the most common cause of PPH. Atony exist when the myometrium cannot contract and cannot control bleeding by constricting the blood vessels. Predisposing causes of atony are: Excessive manipulation of the uterus General anesthesia Uterine overdistension Prolonged labor Grand multiparity Uterine leiomyomas, Previous hemorrhage in the third stage Uterine infection 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.