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In addition to hypertension and infection, obstetrical hemorrhage remains among the infamous triad of maternal death causes. Of more than 7000 pregnancy-related maternal deaths in the United States from 2006 to 2015, hemorrhage was a direct cause in 11 percent (Creanga, 2015, 2017; Petersen, 2019). Hemorrhage is also the single most important cause of maternal death worldwide (Goffman, 2016; Oladapo, 2016). Notably, perhaps a third of severe cases of hemorrhage are likely preventable (Lepine, 2020).

These statistics have prompted several organizations to develop programs to prevent hemorrhage-related maternal morbidity. In the United States, one example is the Alliance for Innovation on Maternal Health (AIM) (2015), with its intent to standardize recognition, response, and reporting of obstetrical hemorrhage. The Joint Commission (2019) has also implemented standards under the Provision of Care, Treatment, and Services chapter for obstetrical hemorrhage—the R3 Report. Our following three chapters align with these.

GENERAL CONSIDERATIONS

Mechanisms of Normal Hemostasis

Near term, an incredible amount of blood—at least 600 mL/min—flows through the spiral arteries and into the intervillous space (Pates, 2010). Averaging 120 in number, the spiral arteries lack a muscular layer because of their remodeling by trophoblasts and thereby form a low-pressure system. With placental separation, vessels at the implantation site are avulsed. Hemostasis is achieved first by myometrial contraction, which directly compresses the arteries. Compression is followed by clotting and eventually by obliteration of vessel lumens.

If, after delivery, the myometrium contracts vigorously, substantial hemorrhage from the placental implantation site is unlikely. Importantly, an intact coagulation system is not necessary for postpartum hemostasis unless there are lacerations in the uterus, birth canal, or perineum. However, fatal postpartum hemorrhage can result from uterine atony despite normal coagulation.

Definition and Incidence

Historically, postpartum hemorrhage has been defined as blood losses ≥500 mL after the third stage of labor. This is problematic because almost half of all women delivered vaginally shed that amount of blood or more when losses are carefully measured. Moreover, approximately 5 percent of women delivering vaginally lose >1000 mL of blood (Fig. 42-1) (Pritchard, 1962). Almost a third of women undergoing cesarean delivery have blood loss >1000 mL. The American College of Obstetricians and Gynecologists (2019a) now defines postpartum hemorrhage as cumulative blood loss >1000 mL or blood loss accompanied by signs and symptoms of hypovolemia.

FIGURE 42-1

Measured blood loss with vaginal delivery, repeat cesarean delivery, and repeat cesarean delivery plus hysterectomy.

In a Maternal-Fetal Network Units study of more than 115,000 deliveries, the incidence of hemorrhage with vaginal delivery was 5.3 percent, and it was 10.5 percent for cesarean delivery (Yee, 2019). Importantly, hemorrhage is underreported. From the National ...

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