Essentials of Diagnosis
- Fetal heart rate abnormalities.
- Increased suprapubic pain and tenderness with labor.
- Sudden cessation of uterine contractions with a "tearing" sensation.
- Vaginal bleeding (or bloody urine).
- Recession of the fetal presenting part.
Rupture
of the pregnant uterus is a potential obstetric catastrophe and a major cause
of maternal death. The incidence of uterine rupture is 0.8% for women with a
prior low-transverse uterine scar and 4–8% for women with a prior classic scar.
Complete rupture includes the entire thickness of the uterine wall and, in most
cases, the overlying serosal peritoneum (broad ligament) (Fig 20–5). Occult
or incomplete rupture is a term usually reserved for dehiscence of a
uterine incision from previous surgery, in which the visceral peritoneum
remains intact. Such defects usually are asymptomatic unless converted to
complete rupture during the course of pregnancy or labor.
Risk factors
Risk factors for uterine rupture include history of
hysterotomy (cesarean section, myomectomy, metroplasty, cornual resection),
trauma (motor vehicle accident, rotational forceps, extension of a cervical
laceration), uterine overdistention (hydramnios, multiple gestation,
macrosomia), uterine anomalies, placenta percreta, and choriocarcinoma.
Ruptures usually occur during the
course of labor. One notable exception is scars from a classic cesarean section
(or hysterotomy), one-third of which rupture during the third trimester before
term and before the onset of labor. Other causes of rupture without labor are
placenta percreta, invasive mole, choriocarcinoma, and cornual pregnancy.
Complete ruptures can be classified as
traumatic or spontaneous. Traumatic ruptures occur most commonly as a result of
motor vehicle accidents, improper administration of an oxytocic agent, or an
inept attempt at operative vaginal delivery. Breech extraction through an
incompletely dilated cervix is the type of operative vaginal delivery most
likely to produce uterine rupture. Other maneuvers that impose risk of rupture
are internal podalic version and extraction, difficult forceps, destructive
operations, and cephalic replacement to relieve shoulder dystocia. Neglected
obstructed labor may be responsible for rupture of the uterus. Causes of
obstructed labor include contracted pelvis, fetal macrosomia, brow or face
presentation, hydrocephalus, or tumors involving the birth canal. The vast
majority of uterine ruptures are associated with prior uterine surgery. Previous
uterine surgery includes both classic and low cervical section, intramural or
submucous myomectomy, resection of the uterine cornu, metroplasty, and
trachelectomy. Other operative procedures that may have damaged the uterus are
vigorous curettage, induced abortion, and manual removal of the placenta.
There are no reliable signs of
impending uterine rupture that occurs before labor, although the sudden
appearance of gross hematuria is suggestive.
Rupture may produce local pain and
tenderness associated with increased uterine irritability and, in some cases, a
small amount of vaginal bleeding. Premature labor may follow. As the extent of
the rupture increases, more pain, more bleeding, and perhaps signs of
hypovolemic shock will occur. Exsanguination prior to surgery is unlikely
because of the reduced vascularity of scar tissue, but the placenta may be
completely separated and the fetus extruded partially or completely into the
abdominal cavity.
By far the most common clinical
setting for rupture of the uterus is rupture of a low cervical scar; this
almost always occurs during active labor. Clearly identifiable signs and
symptoms may be lacking. However 78–90% of patients have FHR abnormalities as
the first sign of rupture. Although it is possible that labor will progress to
the vaginal birth of an unaffected infant, rupture may lacerate a uterine
artery, producing exsanguination, or the fetus may be extruded into the
abdominal cavity. If a defect is palpated in the lower uterine segment following
vaginal delivery, laparotomy may be necessary to assess the damage. Laparotomy
is mandatory if continuing hemorrhage is present. If such a defect is palpated
in a stable patient who does not require exploration, a subsequent trial of
labor is contraindicated.
Although much less common than FHR
abnormalities, other findings of spontaneous rupture during labor are
suprapubic pain and tenderness, cessation of uterine contractions,
disappearance of fetal heart tones, recession of the presenting part, and
vaginal hemorrhage—followed by the signs and symptoms of hypovolemic shock and
hemoperitoneum. Ultrasound examination might confirm an abnormal fetal position
or extension of the fetal extremities. Hemoperitoneum can sometimes be seen on
ultrasound.
The clinical picture depends on the
extent of rupture. Unfortunately, valuable time is often lost because the
rupture was not diagnosed at the time of initial examination. Whenever a newly
delivered patient exhibits persistent bleeding or shock, the uterus must be
carefully reexamined for signs of a rupture that may have been difficult to
palpate because of the soft, irregular tissue surfaces.
Whenever an operative delivery is
performed—especially if the history includes events or problems that increase
the likelihood of uterine rupture—the initial examination of the uterus and
birth canal must be diligent. A dehiscence of the lower uterine segment
contained only by a layer of visceral peritoneum is not an uncommon finding at
time of repeat cesarean section.
Treatment is dictated by clinical
scenario and can range from simply repairing the defect and obtaining
hemostasis to removing the entire uterus. If hysterectomy is deemed necessary,
either total hysterectomy or the subtotal operation can be performed, depending
on the site of rupture and the patient's condition. The most difficult cases
are lateral ruptures involving the lower uterine segment and a uterine artery
with hemorrhage and hematoma formation obscuring the operative field. Care must
be taken to avoid ureteral damage by blind suturing at the base of the broad
ligament. If there is a question of ureteral occlusion by a suture, it is best
to perform cystotomy to observe the bilateral appearance of an intravenously
injected dye such as indigo carmine. If doubt still exists, a retrograde
ureteral catheter can be passed upward through the cystotomy wound.
If childbearing is important and the
risks—both short and long term—are acceptable to the patient, rupture repair
can be attempted. Many ruptures can be repaired. Successful pregnancies have
been reported following uterine repair; however, the risk of rupture in a
subsequent pregnancy is at least as high as the risk with a prior classic
cesarean section. Occult ruptures of the lower uterine segment encountered at
repeat section can be treated by freshening the wound edges and secondary
repair, but the newly repaired incision is at increased risk for rupture, and a
subsequent trial of labor is contraindicated.
Most causes of uterine rupture can be
avoided by carefully selecting patients for trial of labor. Thorough and
well-documented informed consent that includes mention of fetal or maternal
death is needed. The ideal candidate will have a single prior low-transverse
cesarean for a nonrepetitive indication (eg, breech), will have a prior vaginal
delivery, will present in active labor, and will not require augmentation
during labor. The further the characteristics diverge from those of this ideal
patient, the greater the chance of a failed trial of labor and complications
including uterine rupture. Continuous FHR monitoring by fetal scalp electrode
as soon as feasible is the best means of detecting evolving rupture during
labor. Two-layer closure of the uterine incision and increasing interval
between pregnancies appears to decrease the risk of subsequent rupture of the
low-transverse scar.
The complications of ruptured uterus
are hemorrhage, shock, postoperative infection, bladder or ureteral damage,
thrombophlebitis, amniotic fluid embolus, DIC, pituitary failure, and death.
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