Final answer:
Uterine atony is the most common cause of Postpartum Hemorrhage (PPH), where the uterus fails to contract effectively after childbirth leading to excessive bleeding. Retained placental fragments and complications like placenta previa can also lead to PPH, which is why examination by an obstetrician is crucial.
Step-by-step explanation:
The most common cause of Postpartum Hemorrhage (PPH) is the failure of the uterus to contract strongly enough after childbirth, a condition known as uterine atony. The uterus normally contracts to seal off blood vessels where the placenta was attached; however, if these contractions are not strong enough, it can lead to excessive bleeding. It is important that the obstetrician examines the expelled placenta and fetal membranes to ensure that they are intact, as fragments that remain can also provoke hemorrhage. Additionally, complications such as placenta previa and placental abruption can predispose a person to PPH. During the postpartum period, the mother experiences lochia discharge, which is normally limited by postpartum uterine contractions. When breastfeeding, oxytocin is released which also helps in facilitating uterine involution and reducing blood loss.