What signs and symptoms would lead the nurse to suspect a uterine rupture is occurring?

Uterine Rupture

The principal risk associated with TOLAC is uterine rupture. This complication is directly attributable to TOLAC, because symptomatic rupture is rarely observed in planned repeat operations.10,38–41It is important to differentiate betweenuterine rupture anduterine scar dehiscence. This distinction is clinically relevant because dehiscence most often represents an occult scar separation observed at laparotomy in women with a prior cesarean delivery. With uterine dehiscence, the serosa of the uterus is intact and hemorrhage, with its potential for fetal and maternal sequelae, is absent. In contrast, uterine rupture is a through-and-through disruption of all uterine layers, with potential consequences of nonreassuring fetal status and perinatal morbidity and mortality along with severe maternal morbidity, hemorrhage, and mortality. Terminology, definitions, and ascertainment of uterine rupture vary significantly in the existing VBAC literature.39 A review40 of four observational studies reported the risks of symptomatic uterine rupture in the TOLAC group and elective repeat cesarean group to be 0.47% (95% confidence interval [CI], 0.28% to 0.77%) and 0.026% (95% CI, 0.009% to 0.082%), respectively.The large multicenter MFMU Network Study10reported a 0.69% frequency of uterine rupture, with 124 symptomatic ruptures occurring in 17,898 women undergoing TOLAC.

The rate of uterine rupture depends on both the type and location of the previous uterine incision (Table 20.3). Uterine rupture rates are highest with a previous classical or T-shaped incision, with a range reported between 4% and 9%. The risk for rupture with a previous low vertical incision has been difficult to estimate owing to imprecision with the diagnosis and the uncommon use of this incision type. Naif and colleagues42 reported a 1.1% risk for rupture in 174 women with a prior low vertical scar undergoing TOLAC, whereas Shipp and associates45 reported a 0.8% (3 of 377) risk for rupture with a prior low vertical incision. On the basis of these two studies, the authors concluded thatwomen with a prior low vertical uterine incision are not at significantly increased risk for rupture compared with women with a prior low transverse incision.

Women with an unknown incision type do not appear to be at increased risk for uterine rupture. Among 3206 women with an unknown scar in the MFMU Network Cesarean Registry, uterine rupture occurred in 0.5% of those undergoing TOLAC.15 Nevertheless, this frequency is a reflection of the fact that in a contemporary setting, most women with unknown scars will have had a prior low transverse incision.In counseling women with an unknown scar, the physician should attempt to understand whether a prior cesarean delivery had been performed under circumstances in which it was more likely that a different type of incision had been used. For example, a history of preterm cesarean delivery should warrant caution, especially in the setting of malpresentation, because the incision may have involved an undeveloped muscular portion of the uterus or it may have been a classical incision. For these reasons, if the clinician suspects that the prior delivery occurred under circumstances in which an incision that extended into the muscular portion of the uterus was used, we generally proceed with repeat cesarean delivery.

Risk

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Incidence varies: 1/1280–1/3000 for all vaginal deliveries

Incidence of uterine rupture in women with unscarred uterus approx 0.01% in industrialized countries

Incidence of rupture with prior C-section ranges from 0.2–0.8%.

In women with previous upper uterine surgery (myomectomy), incidence of rupture can be as high 1.7%.

Risk factors incl prior uterine scar; rapid, tumultuous labor; prolonged, augmented labor; trauma; and grand multiparity, polyhydramnios

Perioperative Risks

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Potentially catastrophic for mother and fetus. Maternal morbidity is ∼0.1% and incl hemorrhage, shock, and hysterectomy. If fetus delivered within 30 min, fetal morbidity improved but still incl hypoxemia and/or acidosis, depressed apgar scores, and admission to neonatal ICU.

Maternal mortality greatly increased in pts with traumatic or spontaneous rupture likely 2° to delayed suspicion and/or Dx and treatment.

Worry About

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Massive hemorrhage in mother

Fetal hypoperfusion and hypoxemia

Overview

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Due to a breach in the myometrium, which is often 2° to a separation of a previous C-section scar, uterine rupture can occur antepartum, intrapartum, or postpartum. The lower uterine segment, at term, contains mostly connective tissue and little placental tissue. Therefore, most ruptures are asymptomatic and do not result in maternal and/or fetal compromise. However, if placental tissue is involved, massive bleeding with resultant need for emergent C-section and/or laparotomy can occur.

Vaginal delivery is preferred over C-section as maternal blood loss and maternal morbidity are decreased.

ACOG advocates trial of labor after delivery in pts with previous low transverse uterine scar. Mothers with classical C-sections and/or inductions with prostaglandins are both discouraged by ACOG as risk of rupture is greatly increased. As well, trial of labor after C-section is discouraged in hospitals where emergency C-sections cannot be performed within 30 min.

Fetal bradycardia is most common presenting symptom (∼70%). Other Sx incl vaginal bleeding, abd and/or shoulder pain, hypotension and/or shock. Abd pain is still a reliable sign in the presence of an epidural if low-dose concentration local anesthesia is used.

ICD-9-CM Code: 665.1 (Uterine rupture during labor)

Etiology

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Separation of scar from previous C-section, often during trial of labor

Rupture of myomectomy scar (highest incidence of rupture)

Weak or stretched uterine muscles due to grand multiparity, polyhydramnios, or multiple gestations

Precipitous labor or prolonged labor with oxytocin augmentation

Traumatic rupture

Usual Treatment

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When occurring antepartum or during labor, urgent and/or emergent laparotomy with C-section and uterine repair or hysterectomy is the only treatment. Urgency is determined by speed of Dx and maternal and fetal stability.

If diagnosed incidentally postpartum, mother may undergo close observation without surgery.

Uterine Rupture

Uterine rupture is poorly defined and includes cases ranging from scar dehiscence to those with catastrophic uterine wall rupture. In addition to prior uterine scar, uterine rupture is associated with rapid spontaneous delivery, motor vehicle trauma, trauma from instrumented vaginal delivery, large or malpositioned fetus, and excessive oxytocin stimulation. Following a single prior cesarean delivery with a low transverse incision, a trial of labor after cesarean (TOLAC) is associated with a 1% or less incidence of uterine rupture.92 Spontaneous rupture of an unscarred uterus is far more rare. The presentation is variable with no finding being 100% sensitive but may include fetal bradycardia, persistent abdominal pain, vaginal bleeding, cessation of contractions, loss of station, and breakthrough pain with epidural analgesia. Abdominal pain is not always a diagnostic finding, and continuous FHR monitoring indicating deceleration currently represents the most common sign associated with uterine rupture.93 Neuraxial labor analgesia may be used as part of TOLAC and should not be expected to mask signs and symptoms of uterine rupture. Immediate evaluation, aggressive resuscitation, and general anesthesia for emergent cesarean delivery are normally required for management. Often uterine repair by the obstetrician can occur following cesarean delivery if a minor scar dehiscence is present, but hysterectomy is needed for most cases of uterine wall rupture of an unscarred uterus. When vaginal birth is planned after a previous cesarean delivery, it is recommended that “TOLAC be undertaken in facilities with staff immediately available to provide emergency care”93 should a uterine rupture occur. Appropriate staffing considerations include obstetric, anesthesia, pediatric, and nursing personnel.

Uterine Rupture

Both blunt and penetrating injuries can result in uterine rupture, which occurs in approximately 0.6% to 1% of instances of maternal trauma.23,52Uterine rupture most often results from direct abdominal impact and may occur at any gestational age, although the risk increases as the uterus becomes an abdominal organ later in pregnancy.1,70 The risk for uterine rupture is particularly increased for women who have experienced assault.37 Most instances of uterine rupture as a result of maternal trauma are fundal in location.52 Uterine rupture may also result in complete avulsion of the uterine arteries and massive hemorrhage.1 Signs of uterine rupture may range from FHR abnormalities in a hemodynamically-stable patient to maternal cardiovascular instability and hypovolemic shock.52 Uterine rupture carries a poor prognosis for the fetus and requires immediate laparotomy. Whether a hysterectomy is required depends on the extent of the myometrial and vascular injury and to what extent the surgeon feels the uterus can be repaired expeditiously. Since uterine rupture may be associated with massive maternal hemorrhage due to increased uterine vascularity associated with pregnancy, aggressive replacement of red cells and clotting factors is recommended.23 Maternal mortality has been reported to be as high as 10% following traumatic uterine rupture.4

Clinical Manifestations and Diagnosis

Uterine rupture is associated with both fetal and maternal clinical manifestations. Fetal bradycardia with or without preceding variable or late decelerations is the most common clinical manifestation of symptomatic uterine rupture and occurs in 33% to 70% of cases.86 In some circumstances, a loss of fetal station in labor may occur. Maternal clinical manifestations are variable and may include acute vaginal bleeding, constant abdominal pain or uterine tenderness, change in uterine shape, cessation of contractions, hematuria (if extension into the bladder has occurred), and signs of hemodynamic instability.

Uterine rupture is suspected clinically but confirmed surgically. Laparotomy will demonstrate complete disruption of the uterine wall with hemoperitoneum and partial or complete extravasation of the fetus into the maternal abdomen.

Historical/Clinical Background

Uterine rupture is discussed in more detail earlier in this chapter and in Chapter 32. It is mentioned here because on occasion coagulopathy presenting with postpartum hemorrhage is its initial sign, rather than cardiorespiratory collapse.

Risk factors for uterine rupture overlap with those for creta (percreta; see Fig. 33.12) and include high parity and prior cesarean section or uterine surgery.130 Rupture is far more common in a scarred uterus, indicating scar dehiscence as the major pathophysiology. When spontaneous uterine rupture occurs in the absence of predisposing risk factors, the location is usually along the lateral wall of the lower uterine segment, partly because of the relatively thinner myometrium in this location. Rupture can extend inferiorly to involve the cervix or irregularly in lateral and superior directions. Hemorrhage is usually severe, with uterine atony following delivery.

Uterine Rupture

Uterine rupture is defined as separation of all layers of the uterine wall, including the serosa, with abnormal communication between the uterine cavity and the peritoneal cavity. Uterine dehiscence is characterized by incomplete rupture of the uterine wall, usually involving the endometrium and myometrium but with an intact overlying serosal layer. More than 90% of cases of uterine rupture are associated with previous cesarean delivery, more commonly associated with a classic vertical incision (4% to 9%) than with a low transverse incision (1.5%). Uterine rupture may also be seen in the setting of previous myomectomy, uterine malformations, in pregnant patients after major trauma, and rarely in women without any known risk factors at the time of spontaneous vaginal delivery.

Uterine rupture is a catastrophic event with variable clinical presentations ranging from vague symptoms such as uterine tenderness and nonreassuring fetal heart rate to acute maternal hypovolemic shock. Sonography has variable sensitivity for detection of the myometrial defect, but can reveal extrauterine location of the fetus and associated peritoneal hematoma. US can rapidly be done at the bedside in this emergent condition. CT and MRI will show similar findings but will better delineate the site of rupture within the uterine wall. In the postpartum period, the presence of gas within the uterine defect extending from the endometrial cavity to the extrauterine parametrium and the presence of associated hemoperitoneum increase the likelihood of rupture in the appropriate clinical setting.

Causes

In modern obstetrics, uterine rupture is almost always due to the misuse of oxytocic drugs. These are used to initiate and maintain the mother's contractions (see Ch. 12, Augmentation of labour).

Uterine rupture

UTERINE RUPTURE

Uterine rupture may or may not involve significant hemorrhage. Rupture is a rare event in the absence of previous uterine surgery (0.01–0.05%), but has an incidence of ∼1% in women attempting vaginal birth after a previous low transverse cesarean (VBAC). The risk is greater if labor is induced or augmented, particularly with prostaglandins. The classic symptom of uterine rupture is either continuous pain (rather than with contractions) or increasing abdominal pain, but many ruptures now present with evidence of fetal compromise. Lack of descent or recession of the presenting part, vaginal bleeding, or maternal hemodynamic instability in a patient with a previous cesarean should suggest the diagnosis. The treatment is usually surgical delivery.