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Postpartum hemorrhage, or excessive blood loss following delivery, has been variably defined. It is traditionally defined as blood loss greater than 500 mL after vaginal delivery. The American College of Obstetrics and Gynecology (ACOG) defines postpartum hemorrhage as blood loss that results in a decrease in hematocrit of greater than 10 points or bleeding that requires erythrocyte transfusion. A drop in the hematocrit of 10 points corresponds to the 97th percentile of vaginal and 92nd percentile of cesarean deliveries.1 Normal blood loss is believed to be 300 to 500 mL following a vaginal delivery and 900 to 1200 mL following a cesarean section.2 Postpartum hemorrhage can occur at sites within or external to the genitourinary tract (Table 114-1).

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Table 114-1. Anatomic Sites of Postpartum Hemorrhage
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The incidence of postpartum hemorrhage ranges from 3.9 to 11 percent of all pregnancies.1–5 Early postpartum hemorrhage accounts for greater than 90 percent of all cases and occurs within 24 hours of delivery. It is most commonly the result of excessive bleeding from the placental implantation site or trauma to the genital tract. It is associated with a considerable drop in hematocrit and significant maternal complications. Late postpartum hemorrhage occurs more than 24 hours after delivery but before 6 weeks postpartum. It is the result of excessive bleeding from the placental implantation site, endometritis, or a hereditary coagulopathy.1,5 This chapter reviews the pathophysiology of early postpartum hemorrhage, discusses the diagnosis and assessment of postpartum hemorrhage, and concludes with strategies for treatment.

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The most common causes of postpartum hemorrhage are uterine atony (70 to 90 percent), lacerations and genital tract injuries (5 to 8 percent), retained products of conception (3 to 5 percent), and hematologic or coagulopathic abnormalities (< 2 percent). Complete and incomplete uterine inversion is a rare cause of postpartum hemorrhage. Risk factors for uterine atony include high parity, advanced maternal age, multiple gestations, polyhydramnios, use of oxytocin or uterine relaxing agents, macrosomia, chorioamnionitis, prolonged third stage of labor, and uterine overdistention.1 Genital tract injuries include vaginal lacerations, cervical lacerations, lower uterine segment lacerations, vulvar hematomas, vaginal hematomas, uterine rupture, and uterine inversion. Retention of all or part of the placenta can interfere with postpartum uterine contraction and retraction. Hematologic abnormalities include von Willebrand’s disease, disseminated intravascular coagulation, and other less common inherited, congenital, or acquired disorders.

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Measurement of actual blood loss is difficult. The hypervolemia and increase in plasma volume seen in normal pregnancy may partially compensate for the initial blood loss. Visual estimates of blood loss are inaccurate. Weigh all pads for an accurate assessment (1 gm = 1 mL of blood). The signs and symptoms of postpartum hemorrhage include measurable blood loss greater than 500 mL, tachycardia, hypotension, pallor, ...

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