Uncommon associations of rupture are uterine anomalies or multifetal pregnancy (Bankada, 2015; Tarney, 2013; Tola, 2014). Occasionally, focal inherent weakness in the myometrium predisposes to rupture. Examples include anatomical anomalies, leiomyomas, adenomyosis, choriocarcinoma, and connective-tissue defects such as Ehlers-Danlos syndrome (Arici, 2013; Nikolaou, 2013; Noh, 2013; Ramskill, 2014; Sun, 2016).
Rupture of the previously intact uterus during labor most often involves the thinned-out lower uterine segment. When the rent is in the immediate vicinity of the cervix, it frequently extends transversely or obliquely. When the rent forms in the portion of the uterus adjacent to the broad ligament, the tear
FIGURE 41-13 Supracervical hysterectomy specimen showing uterine rupture during spontaneous labor with a vertical tear at the left lateral edge of lower uterine segment.
is usually longitudinal. Although these tears develop primarily in the lower uterine segment, they can extend upward into the active segment or downward through the cervix and into the vagina (Fig. 41-13). In some cases, the bladder may also be lacerated. If the rupture is of suicient size, the uterine contents will usually escape into the peritoneal cavity. If the presenting fetal part is firmly engaged, however, then only a portion of the fetus may be extruded from the uterus. Fetal prognosis is largely dependent on the degree of placental separation and magnitude ;f !ii�tei!�l he!ii;iih�be �!d hypovolemia. In some cases, the overlying peritoneum remains intact, and this usually is accompanied by hemorrhage that extends into the broad ligament to cause a large retroperitoneal hematoma.
Following vaginal delivery in an unscarred uterus, we and others have occasionally encountered cases of an incomplete tear on the inside of the uterus that extends vertically into the active segment and is a source of profuse hemorrhage (Conrad, 2015). These tears are usually not visible from below but are found at the time of hysterectomy for intractable bleeding despite a contracted uterus. Hemorrhage with this type of tear can be torrential, and bleeding is usually not slowed until the uterine artery pedicles are clamped bilaterally.
The varied clinical presentations of uterine rupture and its management are discussed in detail in Chapter 31 (p. 598). In the most recent maternal mortality statistics from the Centers for Disease Control and Prevention, uterine rupture accounted for almost 10 percent of deaths caused by hemorrhage (Creanga, 2015, 2017). Maternal morbidity includes hysterectomy that may be necessary to control hemorrhage. Rates of perinatal mortality and morbidity, which may include severe neurological impairment, are also high (Gibbins, 2015; Porreco, 2009).
Maternal obesity comorbid with uterine rupture is associated with increased rates of adverse neonatal outcomes (Yao, 2017).
Separation of the placenta-either partially or totally-from its implantation site before delivery is described by the Latin term abruptio placentae. Literally translated, this refers to "rending asunder of the placenta," which denotes a sudden accident that is a clinical characteristic of most cases. In the purest sense, the cumbersome-and thus seldom used-term premature separation of the normaly implanted placenta is most descriptive because it excludes separation of a placenta previa.