Uterine Scar Rupture: An Obstetric Emergency

An OverView:

Uterine Scar Rupture, the most rare yet most serious risk of vaginal birth after cesarean (VBAC) is when the scar on the uterus may break open (rupture) during labor.This involves a full-thickness disruption of the uterine wall also involving the overlying visceral peritoneum (uterine serosa).A complete uterine scar rupture is a rare, but potentially serious complication, for both the mother and/or the baby that requires immediate surgical intervention.

The risk for uterine rupture of 0.5% to 0.9% with a low transverse scar have a uterine rupture during a trial of labor and 4% to 9% for women with a prior classical cesarean who labor. Therefore, Women who have a low transverse cesarean scar have a lower risk of rupturing than women who have a vertical incision scar.

Sometimes the scar stretches thin enough to cause a dehiscence or window. This is also known as a silent or incomplete rupture or an asymptomatic separation. In contrast to frank uterine rupture, uterine scar dehiscence involves the disruption and separation of a preexisting uterine scar. Uterine scar dehiscence is a more common event than uterine rupture and seldom results in major maternal or fetal complications.These two entities must be clearly distinguished, as the options for clinical management and the resulting clinical outcomes differ significantly.


Risk Factors:

A woman’s risk of uterine rupture increases with:

  • Each additional uterine surgical scar.The vast majority of uterine ruptures occur in women who have uterine scars, most of which are the result of previous cesarean deliveries. A single cesarean scar increases the overall rupture rate to 0.5%, with the rate for women with 2 or more cesarean scars increasing to 2%.
  • Previous classical or T-shaped incision or extensive transfundal uterine surgery
  • Prior uterine rupture.
  • Previous myomectomy involving the contractile portion of the uterus.
  • Women who have a previous single-layer hysterotomy closure
  • Short inter-pregnancy interval after a previous cesarean delivery
  • Macrosomic fetus in current pregnancy
  • Induction of labour with Prostaglandin

Signs, Symptoms and Diagnosis:

The signs and symptoms of uterine rupture largely depend on the timing, site, and extent of the uterine defect. However, modern studies show that some of these signs and symptoms are rare and that many may not be reliably distinguished from their occurrences in other, more benign obstetric circumstances.

The classic signs and symptoms of uterine rupture are:

  • Fetal distress as evidenced most often by abnormal pattern in fetal heart rate or prolonged, late, or recurrent variable decelerations or fetal bradycardia are often the first and only signs of uterine rupture.
  • Diminished baseline uterine pressure
  • Cessation of uterine contractions
  • Sudden or atypical maternal abdominal pain or tenderness
  • Recession of the presenting fetal part
  • Vaginal bleeding or Hemorrhage
  • Shock

The most consistent early indicator of uterine rupture is the onset of a prolonged, persistent, and profound fetal bradycardia. Other signs and symptoms of uterine rupture, such as abdominal pain, abnormal progress in labor, and vaginal bleeding, are less consistent and less valuable than bradycardia in establishing the appropriate diagnosis.Women interested in planned VBAC should be advised that it should be conducted in a suitably staffed and equipped delivery suite, with continuous intrapartum care and monitoring and available resources for immediate caesarean section and advanced neonatal resuscitation.

The uterine rupture is most appropriately diagnosed on the basis of standard signs and symptoms, because of short time available to diagnose uterine rupture before the onset of irreversible physiologic damage to the fetus, time consuming diagnostic methods and sophisticated imaging modalities have a limited utility.

Role of Ultrasound in assessing the risk of uterine rupture after Cesarean Delivery!

However, various diagnostic techniques have been used to attempt to assess the individual risk of uterine rupture in selected patients. Several reports have suggested that trans-abdominal, trans-vaginal, or sonohysterographic ultrasonography may be useful for detecting uterine-scar defects after cesarean delivery.

Rozenberg et al (1996) found in their study that the risk of a defective scar is directly related to the degree of thinning of the lower uterine segment at around 37 weeks of pregnancy. With a cut-off value of 3.5 mm, the sensitivity of ultrasonographic measurement was 88.0%, the specificity 73.2%, positive predictive value 11.8%, and negative predictive value 99.3%.

Gotoh et al (2000) reported in their study, 17 of 23 women (74%) with lower uterine segment less than 2.0 mm in thickness within 1 week (4 +/- 3 days) before repeat cesarean delivery, intrapartum incomplete uterine rupture developed. The authors concluded that Trans-vaginal ultrasonography is useful for measurement of the uterine wall after previous cesarean delivery.


Complications:

The life-threatening seriousness of uterine rupture can be understood by rapidly happening sequence of events which may include:

    • Possible Maternal Complications: Maternal hemorrhage may occur that may further necessitate the requirement of  blood replacement. Hysterectomy may be indicated in patients with intractable haemorrhage or when uterine rupture sites are multiple thus leading to loss of future childbearing potential. Maternal mortality related to uterine rupture may be attributed to disseminated intravascular coagulation (DIC) or irreversible shock.

 

    • Possible Neonatal Complications: Neonatal outcomes seem to be worst when a fetus is extruded from the uterus into the peritoneal cavity, probably as a result of more extensive disruption of the maternal-placental circulation, which can lead to fetal asphyxia and potential long-term neurologic impairment. Although many infants delivered after uterine rupture do well, management often includes admission to a neonatal intensive care unit and, possibly, mechanical respiratory support.The consequences of unrecognized or poorly managed perinatal emergencies can be devastating, ranging from neurologic impairment to intrauterine fetal death.

Management:

Once diagnosed, management must include:

  • Supportive therapy for mother until surgical intervention can arrest life threatening haemorrhage. The physician should ensure adequate intravenous access, arrange for sufficient blood transfusion, and call for a neonatal team to be ready for intensive-care newborn resuscitation. Proper supportive and resuscitation methods should be initiated to help preventing the maternal exsanguination and maternal death.

 

  • Because the presenting signs of uterine rupture are often nonspecific, the initial management of uterine rupture will be the same as that for other causes of acute fetal distress. Emergency cesarean delivery is indicated in view of immediate threat to life of woman and fetus as it may prevent serious fatal and maternal morbidity and mortality. After fetus is delivered the type of surgical treatment for mother depends on factors such as type of uterine rupture, extent of uterine rupture, degree of haemorrhage and mother’s general condition.

 

Due to inconsistent premonitory signs and symptoms of uterine rupture and short time for instituting definitive therapeutic action, uterine rupture in pregnancy can be much feared and challenging event for medical practitioners.