Williams Manual of Pregnancy Complications, 23 ed.

CHAPTER 19. Uterine Rupture of the Unscarred Uterus

Spontaneous rupture of the unscarred uterus is a rare but catastrophic obstetric complication associated with high rates of both maternal and perinatal morbidity and mortality. The occurrence is estimated at 1 in 15,000 or fewer deliveries. Risk factors for rupture of the unscarred uterus include women of high parity and stimulation of labor with oxytocin or prostaglandins and are listed in Table 19-1.

TABLE 19-1. Risk Factors for Rupture of the Unscarred Uterus

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Rupture of the uterus unscarred by prior Cesarean delivery most often occurs in the thinned-out lower uterine segment during labor. Although developing primarily in the lower uterine segment, it is not unusual for the laceration to extend further upward into the body of the uterus or downward through the cervix into the vagina. At times, the bladder may also be lacerated. The reader is referred to Chapter 18for discussion of uterine rupture in women with a prior cesarean delivery.

CLASSIFICATION

Uterine rupture is typically classified as either complete with separation of all layers of the uterine wall (myometrium and peritoneum) or incomplete when the uterine muscle is separated but visceral peritoneum remains intact. Incomplete rupture is also commonly referred to as uterine dehiscence. As expected, morbidity and mortality are appreciably greater when rupture is complete. Currently, the greatest risk factor for either complete or incomplete uterine rupture is a prior cesarean delivery or prior uterine surgery.

CLINICAL COURSE

Prior to circulatory collapse from hemorrhage, the symptoms and physical findings may appear bizarre unless the possibility of uterine rupture is kept in mind. For example, hemoperitoneum from a ruptured uterus may result in irritation of the diaphragm with pain referred to the chest—leading one to a diagnosis of pulmonary or amnionic fluid embolus instead of uterine rupture.

Although once taught, it appears that few women experience cessation of contractions following uterine rupture. Instead, the most common electronic fetal monitoring finding tends to be sudden, severe heart rate decelerations that may evolve into late decelerations, bradycardia, and then undetectable fetal heart action. While in some women, the appearance of uterine rupture is identical to that of placental abruption; in others, there is remarkably little appreciable pain or tenderness. Also, because most women in labor are treated for discomfort with either narcotics or lumbar epidural analgesia, pain and tenderness may not be readily apparent. The condition usually becomes evident because of signs of fetal distress, maternal hypovolemia from concealed hemorrhage, or both.

In some cases in which the fetal presenting part has entered the pelvis with labor, there is loss of station detected by pelvic examination. If the fetus is partly or totally extruded from the uterine rupture site, abdominal palpation or vaginal examination may be helpful to identify the presenting part, which will have moved away from the pelvic inlet. A firm, contracted uterus may at times be felt alongside the fetus.

MANAGEMENT

A high index of suspicion and prompt recognition followed by an emergent laparotomy in combination with vigorous blood and fluid replacement are necessary to minimize the catastrophic consequences of uterine rupture. Following delivery of the infant, clinical circumstances dictate either repair of the uterine defect versus hysterectomy.

PROGNOSIS

With uterine rupture and expulsion of the fetus into the peritoneal cavity, the chances for intact fetal survival are poor, and mortality rates reported in various studies range from 50 to 75 percent. If the fetus is alive at the time of the rupture, the only chance of continued survival is afforded by immediate delivery; otherwise, hypoxia from both placental separation and maternal hypovolemia is inevitable.


For further reading in Williams Obstetrics, 23rd ed.,

see Chapter 26, “Prior Cesarean Delivery.”