Postpartum Haemorrhage (PPH) is excessive bleeding following childbirth and is one of the major causes of maternal mortality worldwide.
The most common cause of PPH is uterine atony, which means the uterus fails to contract properly after delivery.
When the uterus does not contract, the blood vessels that supplied the placenta remain open and continue to bleed heavily.
Traumatic causes like tears or lacerations can lead to PPH but are less common than uterine atony.
Retained placenta can also cause PPH if parts of the placenta remain attached and prevent uterine contraction.
However, Atonic Uterus remains the leading cause and primary factor in most cases.
Therefore, the correct answer is Atonic Uterus.