Background

Uterine rupture(UR) is a serious complication that directly jeopardizes the life of the mother and the fetus [1]. It refers to the rupture of the uterine body or the lower uterine segment in late pregnancy or during labor [2], requiring a cesarean section to terminate the pregnancy as soon as the diagnosis is confirmed. The most common risk factors of UR are a history of previous cesarean section (CS), myomectomy, multiparity, malpresentation, breech extraction, and instrumental deliveries [3].

The incidence of uterine rupture in China has recently been reported to range from 0.1% to 0.55% [4]; although this incidence rate is low, UR is highly likely to lead to serious adverse outcomes.

Currently, there are no effective means for detecting or predicting the weakest points of the uterus. Therefore, in this study, we aimed to provide reference information and practical experience for the early recognition, management and emergency treatment of uterine rupture.

Methods

The Department of Obstetrics and Gynaecology of the First people’s Hospital of Chenzhou is a critical care center wherein treatment, consultation, referral, and technical guidance are proviede to pregnant women in Southern Hunan and the city with acute and critical illnesses. This was a retrospective study aimed at exploring the clinical characteristics, treatment, and prognosis of patients with complete uterine rupture between January 2015 and December 2022. The data (complete clinical data, medical history, and surgical records) of all patients with complete uterine rupture admitted to our hospital were retrospectively analyzed.

Diagnostic criteria

Complete uterine rupture was defined as rupture of the entire wall of the uterine myometrium, with the uterine cavity communicating with the abdominal cavity during late pregnancy or labor [1].

Postpartum hemorrhage (PPH) was defined as bleeding of ≥ 500 ml for vaginal delivery and ≥ 1000 ml for cesarean delivery within 24 h after delivery of the fetus [1].

Research methods

Basic maternal information (age, pregnancies, number of deliveries), previous pregnancy and surgery-related indicators (risk factor, causes and clinical manifestations, comorbidities, distance between periconceptional caesarean section scar and vesicovaginal fold), situation at the time of uterine rupture (gestational age, interval between the current pregnancy and previous cesarean section delivery, rupture site and length, bleeding volume and number of required blood transfusions, minimum hemoglobin level), mode of the current delivery (induced delivery, transvaginal delivery, or cesarean section), and outcomes of the mother and child (postpartum hemorrhage, hysterectomy, maternal death, perinatal deaths, severe neonatal asphyxia (Apgar scores are recorded at 1, 5, and 10 min after birth, with a score below or equal to 3 indicating severe asphxia) were cllected from the patients’ medical records. This study meticulously adheres to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement guidelines.

Results

General information

This was a retrospective study aimed at exploring the clinical characteristics, treatment, and prognosis of all patients with complete uterine rupture between January 2015 and December 2022. The data (complete clinical data, medical history, and surgical records) of all patients with uterine rupture admitted to our hospital were retrospectively analyzed. Thirty-three patients with surgically confirmed complete uterine rupture were included into the study.

Incidence of uterine rupture in our hospital

The total number of pregnant women who delivered in our hospital during the study was 31,555, with 33 cases of complete uterine rupture, accounting for approximately 0.1%(Table 1). The average gestational age at complete uterine rupture was 31+4 weeks (13+1–40+3 weeks), and the average bleeding volume was 1896.97 ml (200–6000 ml) (Table 2).

Table 1 Deliveries in our hospital from January 2015 to December 2022
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Table 2 Data of 33 cases of complete uterine rupture
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Causes of uterine rupture

The causes of uterine rupture are shown in Table 3. Ten patients (30.3%) had a history of cesarean section and rupture at an incision site other than the original cesarean section. Patient 2 was involved in a car accident. Patient 11 underwent an elective cesarean section, and uterine rupture was found intraoperatively: the blood flow around the rupture was not rich, the bleeding was not much, and there were no obvious symptoms. Patient 14 had a history of laparoscopic right tubal surgery with poor symptomatology due to adhesion coverage. Patient 16 had a history of cesarean section and wedge resection of the right uterine horn (> 5 years prior), two artificial abortions (AA2), and one induction of labor in middle pregnancy (20+ weeks gestation, fetal anomaly, postpartum evacuation), with poor symptomatology due to adhesion coverage. Patient 27 has a cesarean section after transabdominal cerclage (intraoperative discovery of placental implantation), with uterine rupture in the cerclage line. Patient 33 had a history of two cesarean sections; this time, she was treated with ritodrine for fetal preservation and low molecular heparin in an outside hospital due to the presence of contractions, small vaginal bleeding, fast heart rhythm, and incomplete suppression of contractions, which were not taken seriously. She was transferred to our hospital for shock and stillbirth where she underwent an emergency cesarean section.

Table 3 Classification of causes of complete uterine rupture in 33 cases
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Six patients (18.18%) had a history of uterine operation. Patient 17 had a history of one AA and two vaginal births (VB). She was involved in coitus multiple times in the week prior to the delivery, and the night before delivery, resulting in premature rupture of the membranes; she did not notify the medical staff, and the labor did not come to term. The cervical canal did not open, HS-1 (the lowest point of the fetal skull is 1 cm below the sciatic ischiadica), and 10 min after using oxytocin, cervical dilatation was at 3 cm. Oxytocin was discontinued once abnormal fetal presentation was observed. A cesarean section was performed immediately fetal heart monitoring revealed a deceleration. Patient 20 underwent a breech vaginal trial of labor, with difficulty delivering the fetal head, vaginal rupture, and uterine rupture.

Clinical signs and symptoms of uterine rupture

The clinical signs and symptoms associated with complete uterine rupture are shown in Table 4.

Table 4 Apparent clinical signs and symptoms associated with complete uterine rupture
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There were a few special cases. Patient 1 had an intellectual disability and was unable to express her discomfort accurately. Patient 25 had a metal ring at the breach site. Patient 10 had a cesarean scar pregnancy (CSP) with abdominal blood accumulation (mass) of approximately 3200 ml. Four (12.21%) placental implantation at the incision sites. Three patients presented with severe postpartum hemorrhage, and two of them underwent hysterectomies. The third patient had a repeat vaginal delivery after three VB, two cesarean sections (CS), and one vaginal birth after cesarean (VBAC), and was transferred to our hospital with hemorrhage after delivery; intraoperative rupture of the original cesarean section incision and placenta implantation at the rupture site were observed. Patient 21 had a post-VBAC.

Treatment of uterine rupture and maternal and fetal outcomes

The fetal outcomes and treatment of uterine rupture are shown in Table 5. Postpartum hemorrhage did not occur in 11 patients (33.33%); six (18.18%) were found to have uterine rupture during full-term, elective surgery, with little blood flow around the rupture, and little bleeding with no obvious symptoms. Two patients (6.06%) had severe adhesions. One (Patient 21) was promptly delivered by cesarean section due to abnormal fetal heart rate monitoring; and two (Patients 28 and 29) had uterine tenderness after ethacridine administration and promptly underwent cesarean section.

Table 5 Treatment and maternal and fetal outcomes
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Discussion

Incidence of complete uterine rupture

Since the opening of the separate two-child policy in 2013, full liberalization of the two-child policy in 2016, and opening of the three-child policy in 2021, the cesarean section rate in China has increased from 34.9% (2014) to 41.1% (2016) [15]. Following this, the rate of scarred uterus has increased from 9.8% (2012) to 17.7% (2016) [16], which is far beyond the World Heallth Organizations ideal range.

The incidence of uterine rupture has been reported in several countries and regions; it is not consistent across countries and regions. This rate is related not only to the high-risk factors of the pregnant women themselves, but also to the economic level of each country, number of years of occurrence (which is related to the country's policy at that time), level of medical care, and transportation status (referral time). The reported incidence of uterine rupture: is 0.06% in Northern Europe [17], 0.67% in the University of Pakistan Teaching Hospital [18], 0.01% in the First Maternity and Infant Hospital of Shanghai [19], 0.2% in the Jiangxi Maternity and Child Healthcare Hospital [20], and 0.05% in the Women's Hospital of the Medical College of Zhejiang University [21]. Following the latest data [22], the total incidence of uterine rupture in China is 0.13%, consistent with 0.1% found in this study.

Analysis of the etiology and risk factors for complete uterine rupture

Due to the low cesarean section rate and the large number of patients with two or multiple deliveries between 1960 and 1990, uterine rupture was the predominantly primary. After 1990, with the implementation of family planning policies, the cesarean section rate increased, and subsequently, cesarean section scar rupture became the primary cause of uterine rupture [23]. Therefore, with the improvement in medical standards, doctors' awareness of uterine rupture, and repeated emergency drills, the main etiology has changed.

The known etiologies and risk factors for uterine rupture are as follows [1, 23].

  1. (1)

    Previous uterine injury or history of abnormalities.

A history of myometrial surgery and short or long intervals between surgeries, which include cesarean section (incidence of uterine rupture was 0.071% [21], 0.095% for a history of one cesarean Sect [24]., and 1.92% for a history of two or more cesarean Sects [24].), history of repair of uterine rupture (33% [25]), myomectomy, wedge resection of the uterine horn (incidence of uterine rupture is up to 30% [26]), tubal surgery, hysteroscopic septum resection (incidence of uterine rupture is 1.0%–2.7% [27, 28]), and separation of adhesions in the uterine cavity. Human Immunodeficiency Virus (HIV) infection may increase the incidence of cesarean delivery complications [29]. Current research suggests that the uterine wound healing takes 12 weeks [30], while myometrial incision healing and scar formation takes 6–12 months [31]; however, wound healing does not mean that it is able to withstand the pressure of pregnancy immediately. It also undergoes a process of tissue reconstruction, which further strengthens the elasticity of the uterine myometrial wall in the area of the scar. Therefore, less than 12–18 months is a high-risk factor for uterine rupture [32], and 2–3 years after cesarean section is the optimal period for uterine incision healing [33]. After > 5 years [6], the uterine scar’s degree of muscularization will gradually deteriorate and it will lose elasticity, making uterine rupture more likely during another pregnancy. The risk of uterine rupture for second pregnancies has been reported in the literature, even when tubal surgery does not involve the mesosalpinx or uterine horn, with a higher risk in the presence of electrocoagulation injuries, injury to or absence of part of the myometrial layer of the uterine horn, localized unsutures, and short intervals between pregnancies. The incidence of uterine rupture in our study was 0.79 per 1000 in those with a history of cesarean section, 0.057% in those with a history of one cesarean section, and 0.022% in those with a history of two or more cesarean sections. In our study, 11 patients (33.33%) had an interval of pregnancy out of 1.5 and 5 years, two (6.06%) had a history of tubal surgery, one (3.03%) had a history of wedge resection of the uterine horn, and one (3.03%) was a person living with HIV. It is important to note that in patients with a history of uterine rupture, the rupture was not at the same location. Uterine injuries include abortion, curettage, as well as sharp or blunt contusions such as car accidents, knives, and hidden uterine ruptures. In the present study, six (18.18%) patients had a history of intrauterine manipulation as a risk factor. Congenital abnormalities include uterine dysplasia, and connective tissue defects. In the present study, two patients (6.06%) had a double uterus. Furthermore, one patient (case 7) had a history of transabdominal cervical cerclage. During pregnancy, the cerclage line increases with the uterus, creating a chronic transverse cutting effect on the cervix, Uterine rupture occurs at the site of the cervical cut once there is significant uterine contraction.

  1. (2)

    Combined uterine injuries or abnormalities in this pregnancy

  • Postnatal etiologies include advanced age, muliple pregnancies and deliveries, spontaneous tonic uterine contractions, excessive contractions due to the use of oxytocin or prostaglandins and maternal sensitivity to drugs, prostaglandin or saline intra-amniotic infusion, sharp forceps contusion, external inversion, amniotic fluid overload, or multiple pregnancies. In this study, one patient (3.03%) was treated with uterotonics and three (9.09%) underwent induction of labor.

  • Intrapartum etiologies include any mechanism leading to obstruction of fetal descent, such as pelvic stenosis, cephalopelvic disproportion, obstruction of the soft birth canal, abnormal fetal position, and macrosomia; internal inversion; forceps delivery; emergency labor; breech traction; fetus destruction; excessive dilatation of the uterus in the lower part of the uterus caused by fetal anomalies; excessive pressure in the uterine cavity during delivery; implantation of the placenta or severe adhesion; and difficulty in manually stripping the placenta. One patient (case 20) in this study had uterine rupture due to breech traction during vaginal delivery and eight (24.24%) had placenta implantation.

  • Acquired etiologies include gestational trophoblastic disease, adenomyosis, posterior flexion uterine implantation, and uterine artery embolization surgery. One patient in this study had adenomyosis.

  • CSP involves a poorly healed uterine incision, wide scarring, and inflammation, leading to the development of microscopic fissures through which the fertilized ovum is deposited into the myometrium. Most cases have a poor prognosis [1]. Only one case of CSP was reported in this study.

  • Placental implantation: when it occurs at the site of the original cesarean section scar is caused by a structural defect in the endometrium [23] that allows the placenta to attach abnormally to the uterine myometrium. In our study, four patients (12.12%) had placental implantation, with three who had severe postpartum hemorrhage and two who underwent hysterectomies.

  • Trial of labor after cesarean (TOLAC), during a second pregnancy or request for a vaginal trial of labor; A meta-analysis showed that TOLAC results in a 0.27% higher risk of uterine rupture [9]. The management of TOLAC is a multifactorial. Factors [34, 35] such as a previous vaginal delivery, use of epidural anesthesia, indication for previous cesarean section, pregnancy complications (such as preeclampsia, and placental anomalies), fetal weight above 4000 g, dose of oxytocin used, induction of labor with prostaglandins, women who delivered at > 41 +0 weeks of gestation, ethnicity, cervical length, head-perineum distance, maternal age (maybe), inter-delivery interval, body mass index (maybe), and prolonged second stage of labor (maybe) contribute to uterine rupture during TOLAC. However, there are no data or literature supporting whether to perform a TOLAC and assess the risk of uterine rupture in a second pregnancy after a history of two cesarean deliveries and after one VBAC.

  1. (3)

    Others

Endometriosis causes tissue adhesions. Surgical separation of these adhesions results in localized myometrial destruction and thinning, affecting the healing, brittleness, and elasticity of the scar. Patient 6 had this clinical presentation. It has also been shown that the distance from the cesarean scar to the vesicovaginal fold (suggestive of the horizontal position of the uterine incision from the previous cesarean section) is significantly increased in patients with a gestational age > 22 weeks and antepartum uterine rupture, and may be predictive of uterine rupture [9].

Regardless of how the uterus is damaged, scarring occurs during the repair process, which constitutes non-normal muscle tissue (connective and scar tissue) [1]. This forms a weak site of the uterus during pregnancy. We obseerved that uterine rupture occurred at a random site, mainly at the weakest point of the uterus. There is no effective means for detecting or predicting the weakest point of the uterus. In addition, the uterus may have ruptured in more than one location (Patient 2 had three ruptures).

Clinical manifestations and early diagnosis of uterine rupture

In general, most uterine ruptures progress from uterine rupture precursors, with the main clinical manifestations being abdominal pain (especially during the intervals between contractions), uterine tenderness (reported in the literature to be approximately 36.0% [21]), fetal abnormalities, abnormal vaginal bleeding, pathological contractions, hematuria, disappearance of contractions, hemodynamic instability (tachycardia, hypotension, or shock), change of fetal position, signs of uterine rupture detected by ultrasound, and changes in abdominal contour [1]. Some symptoms are asymptomatic; however, typical symptoms are rare (less than 10% [36]). Currently, pregnancy relies on the co-monitoring of history, clinical presentation, signs, and ultrasonography or magnetic resonance imaging (MRI). It is very difficult to rely on pregnancy management to prevent uterine rupture, which may be due to the following: the timing of uterine rupture is random, the rupture may be unrelated to the original surgical site, most patients have multiple risk factors, and the weakest part of the uterus may change with gestational age and cannot be predicted in advance. The time window for uterine rupture is difficult to control. The time may be longer in patients with thick abdominal fat and varying pain tolerance. If referral is required (long travel time), the optimal time for resuscitation is easily delayed. Abdominal pain, fetal distress, and vaginal bleeding do not allow us to initially consider uncommon uterine ruptures. Clinicians have limitations in considering abdominal pain, which is prone to misdiagnosis as other acute abdominal conditions or labor precursors. Furthermore, multiple pregnancies, literacy levels, and family economic status may lead to irregularities during obstetrical tests. Uterine rupture most often occurs suddenly most ofter, with immediate surgery performed upon diagnosis, failure to achieve continuous fetal heart monitoring, or fetal death at the time of presentation. Other conditions that do not directly lead to uterine rupture but can interfere with early recognition, such as mental retardation, history of frequent coitus, history of abdominal trauma, unawareness of the condition by family members (inability to provide an accurate history when the patient is in shock), use of ritodrine (rapid heart rate) and vomiting during pregnancy, can mask the early signs of shock. Color ultrasonography and MRI can be affected by the level of the examiner, thickness of abdominal fat in the pregnant woman, measurement site, number of measurements, bladder filling, rupture site (posterior wall rupture is difficult to diagnose), fetal movement, dynamic monitoring or not, and clarity of the ultrasound machine. In addition, the presence of unknown previous surgery (inverted T-shaped incision, uterine monolayer suture, weak local myometrium, infection, poor healing of incision, cause of postpartum hemorrhage, and method used to stop bleeding), diverticulum of the uterine incision (occurs in approximately 60% of patients after a primary cesarean section and 100% after three cesarean Sects [37].), any perforation during uterine manipulation, artificial placental removal during previous delivery, and subsequent follow-ups can affect the diagnosis of uterine rupture. In particular, the healing of the original cesarean section scar is unknown; a study showed that the use of synthetic absorbable monofilament sutures for uterine closure was associated with increased residual myometrial thickness, with respect to synthetic absorbable multifilament sutures. A uterine segment thickness after cesarean section below 2.0 mm between 35 and 38 gestational weeks has been repetitively associated with a greater risk of uterine rupture or scar dehiscence [37]. Furthermore, when the breach is small and there are no blood vessels at the breach, there may be no obvious symptoms or imaging changes. Atypical symptoms, difficult diagnosis of intra-abdominal hemorrhage, and unsupportive ancillary tests plague surgical decision-making. There is limited data on some factors that may affect the healing of the uterine incision [23] (previous history of postpartum hemorrhage, gestational diabetes mellitus or diabeties as a comorbidity, embryo transplantation, hypertensive disorders of pregnancy, and hypoproteinemia), and factors that may provide local protection, such as the severity of the pelvic-abdominal adhesions (three patients in this study had little hematochezia or peritoneal hemorrhage). Therefore, the education of pregnant women and their families, as well as the rapid recognition of uterine rupture after it occurs, are key to early diagnosis. 

Complications of complete uterine rupture

Uterine rupture can cause severe postpartum hemorrhage, shock, disseminated intravascular coagulation, impaired organ function (ischemia–reperfusion), bladder injury, massive blood transfusion, hysterectomy, maternal death, neonatal asphyxia, ischemic-hypoxic encephalopathy, perinatal death (fetal or neonatal death), and other serious adverse outcomes.

Conclusions

Good prenatal and pregnancy care (contraceptive promotion, previous surgical records, control of diet weight gain, etc.), graded management (all women need to be risk-graded, strict control of high-risk factors, and timely referral), and early hospitalization of patients with high-risk factors for uterine rupture are key to the early diagnosis and treatment of uterine rupture. For patients with reproductive requirements, strict control of surgical indications, strengthening of suturing skills, guidance on postoperative precautions, strict control of indications for uterotonics and close monitoring are important. Correct management of the labor process, mastery of the indications for obstetric surgically assisted delivery and operation norms, and strict inspection during surgery (e.g., abdominal cervical cerclage patients to check the integrity of the lower segment of the uterus in the posterior wall) are also required. Regardless of high-risk factors, vigilance for uterine rupture, early recognition, proactive management, and training of rapid response teams should be strengthened to achieve favorable maternal and fetal outcomes.