accompanies up to a fourth of vaginal deliveries. The amounts and proportions for cesarean delivery are much greater. And, � £ hemorrhage is underreported. For example, data from the
O.
postpartum hemorrhage incidences of only 2.0 and 2.6 per cent for two epochs in the United States (Berg, 2009). Similar incidences have been reported by others (Kramer, 2013; Mehrabadi, 2013; Patterson, 2014).
Numerous clinical circumstances raise the risks for obstetrical hemorrhage. he imposing list shown in Table 41-2 illustrates that hemorrhage can manifest at any time throughout pregnancy, delivery, and the puerperium. Thus, any description
TABLE 41 -2. Obstetrical Hemorrhage: Causes, Predisposing Factors, and Vulnerable Patients
Anesthesia or analgesia Halogenated agents Conduction analgesia with
Previous uterine atony Parity: primiparity, high parity
Acute fatty liver Anticoagulant treatment Congenital coagulopathies Amnionic fluid embolism Prolonged retention of
Cause of hemorrhage
FIGURE 41-2 Contributions to maternal death from various causes of obstetrical hemorrhage. Percentages are approximations because of different classification schemata used. DIC = nated intravascular coagulopathy. (Data from AI-Zirqi, 2008; Berg, 201o0; Creanga, 201o5; Zwart, 2008.) of obstetrical hemorrhage should include gestational age. Contributions to maternal death from some of these causes of are shown in Figure 41-2.
Obstetrical hemorrhage is traditionally classified as antepartumsuch as with placenta previa or placental abruption, or as pospartum-commonly caused by uterine atony or genital tract lacerations. In individual women, however, these terms are nonspeciic, and it is reasonable to speciy the cause and gestational age as descriptors.
to its cause. Many aspects of bleeding during the first half of pregnancy from abortion or ectopic pregnancy are covered in
Chapters 18 and 19. Discussions that follow concern pregnan cies with a viable-size fetus. In these cases, rapid assessment should always consider the deleterious etal fects ofmaternal hemorrhage.
During active labor, slight vaginal bleeding is common. This "bloody show" is the consequence of efacement and dilation of the cervix, with tearing of small vessels. Uterine bleeding above the cervix, however, is concerning. It may follow some separation of a placenta previa implanted in the immediate vicinity of the cervical canal, or it may be from a placental abruption or uterine tear. In some women, especially with a placenta previa, cervical varicosities may bleed (O'Brien, 2013). Rarely, there may be velamentous insertion of the umbilical cord, and the involved placental vessels may overlie the cevix-vasa previa. In this case, serious fetal hemorrhage follows laceration of these vessels at the time of membrane rupture (Swank, 2016).
N ear term in many women, the source of uterine bleeding is not identified, bleeding ceases, and no apparent anatomical cause is found at delivery. In most of these cases, bleeding likely originated from a slight marginal placental separation. Despite this, any pregnancy with antepartum bleeding remains at higher risk or an adverse outcome even though bleeding has stopped and placenta previa has been excluded sonographicaly.
Injuries to the Birth Canal