What causes postpartum vaginal delivery (PVD) hemorrhage?

From the Guidelines

The most common cause of postpartum hemorrhage (PPH) is related to uterine atony or lack of effective uterine contraction after delivery, which is typically a clinical diagnosis in >75% of patients 1. This condition is often treated with uterine massage and uterotonic drugs such as oxytocin, and the majority of patients respond well to these treatments. If there is no response, additional considerations would include associated retained products of conception (RPOC), adherent placentation, or even uterine inversion, and in these situations, imaging may be helpful 1. Other causes of PPH include trauma-related hemorrhage, which may be due to lacerations, uterine rupture, or incision extensions, as well as coagulopathy, either inherited or acute related to amniotic fluid embolism, placental abruption, severe pre-eclampsia or hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome 1. It is essential to note that the diagnosis and management of PPH require a multidisciplinary approach, including obstetricians, radiologists, and other healthcare professionals, to ensure the best possible outcomes for patients 1. Key concepts in managing uncontrolled hemorrhage include treating the patient based on clinical presentation, keeping the patient warm, rapidly transfusing, and transfusing packed red blood cells, fresh frozen plasma, and platelets in a fixed ratio 1.

Some of the key factors to consider in the setting of hemorrhage and placenta accreta spectrum include:

• Patients should be kept warm because many clotting factors function poorly if the body temperature is less than 36 °C
• Acidosis should be avoided
• If blood loss is excessive, often defined as estimated blood loss of 1,500 mL or greater, prophylactic antibiotics should be re-dosed
• Laboratory testing is critical to the management of obstetric hemorrhage, including baseline assessment at the initiation of bleeding, which should include platelet count, prothrombin time, partial thromboplastin time, and fibrinogen levels 1.

Overall, the management of PPH requires a comprehensive approach that takes into account the underlying causes of the condition, as well as the patient's overall health and clinical presentation. The most effective treatment for PPH is often a combination of uterine massage, uterotonic drugs, and other interventions, such as surgical procedures or embolization, as needed 1.

From the FDA Drug Label

Postpartum Oxytocin Injection, USP (synthetic) is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage. The cause of PVD hemorrhage is not directly stated in the provided drug labels.

• The labels discuss the use of oxytocin and methylergonovine in managing postpartum bleeding or hemorrhage, but do not specify the cause of the hemorrhage. 2

From the Research

Causes of Postpartum Hemorrhage

• Uterine atony, or failure of the uterus to contract following delivery, is the most common cause of postpartum hemorrhage 3
• Retained placental tissue, lacerations to the genital tract, and coagulation disorders are other causes of postpartum hemorrhage 4
• Uterine atony is more likely in women who have had a general anaesthetic or oxytocin, an over-distended uterus, a prolonged or precipitous labour, or who are of high parity 4
• The Four T's mnemonic can be used to identify and address the four most common causes of postpartum hemorrhage: uterine atony (Tone), laceration, hematoma, inversion, rupture (Trauma), retained tissue or invasive placenta (Tissue), and coagulopathy (Thrombin) 5

Risk Factors for Uterine Atony

• General anaesthetic or oxytocin 4
• Over-distended uterus 4
• Prolonged or precipitous labour 4
• High parity 4

Management of Postpartum Hemorrhage

• Active management of the third stage of labor should be used routinely to reduce the incidence of postpartum hemorrhage 5
• Use of oxytocin after delivery of the anterior shoulder is the most important and effective component of this practice 5
• Oxytocin is more effective than misoprostol for prevention and treatment of uterine atony and has fewer adverse effects 5
• Rapid team-based care minimizes morbidity and mortality associated with postpartum hemorrhage, regardless of cause 5
• Massive transfusion protocols allow for rapid and appropriate response to hemorrhages exceeding 1,500 mL of blood loss 5