Causes:

Uterine atony: It is condition in which the uterine corpus does not constrict propewrly, allowing continued blood loss from the placental site.

• Risk factors for atony include the following: Over distended uterus like in multiple gestation, fetal macorsomia, hydramnios.
• Fatigued uterus as in augmented or prolonged, amnionitis.
  
• Obstructed uterus like in retained placenta or fetal parts, placenta accrete.

The second most frequent cause is trauma to the uterus, cervix, and/or vagina. Risk factors for trauma include the following:

• Disorders of coagulation and Delivery of a large infant
• Instrumentation or intrauterine manipulation (eg, forceps, vacuum)
• Vaginal birth after cesarean section (VBAC)
• Episiotomy
• thrombocytopenia,
• preexisting or occurring during the second or third stage of labor, may be associated with excessive bleeding.
• Trauma during delivery may result in hematomas in the perineum or pelvis. These hematomas may be palpable and should be suspected if the patient has unstable vital signs and little or no external bleeding.
• Uterine inversion may be associated with hemorrhage of approximately 2 L.
• Uterine rupture may be associated with little vaginal bleeding, but it should be considered in the presence of severe abdominal pain and unstable hemodynamic findings.
  

Other risk factors for PPH include the following:

• Preeclampsia
• Previous PPH
• Asian or Hispanic ethnicity
• Nulliparity or multiparity.
  

If hemorrhage does occur there are several steps which can be taken to treat the bleeding, steps used depend on the reason for the bleeding:

• Uterine massage
• Have the mother in the trendelenberg position (Feet above heart)
• Give oxygen
• Ensure two large IV sites are available
• Give Medications (Several types: Pitocin, methergine, hemabate)
• Consider surgery including ligation of Uterine and Hypogastric arteries and/or hysterectomy (removal of the uterus).