Silent Danger: Risk Factors and Outcomes of Fortuitously Discovered Uterine Rupture – A 41-Case Cohort Study

Introduction

Uterine rupture (UR) is still a significant cause of injury in the obstetrician’s field, it is particularly prevalent in low-income settings and contributes to the majority of maternal morbidity.¹ While typically detected during labor via classic symptoms, emerging evidence suggests that a subset of UR cases are likely to remain clinically silent.² These asymptomatic discoveries, which were made during imaging or surgery, represent a significant knowledge deficiency in the assessment of obstetric risks.^3–5

Although most URs occur in previously scarred uteri, rare etiologies have been reported in unscarred uteri, including uterine anomalies, connective tissue disorders, or placenta accreta spectrum disorders such as placenta percreta.⁶

In developing countries, several studies have addressed silent or symptomatic UR. For example, Ebeigbe et al. (Nigeria),⁷ Kadowa (Uganda)⁸ and Fofie & Baffoe (Ghana)⁹ documented how healthcare access, sociocultural factors, and surgical history affect UR incidence.

In Tunisia, 1.5% of pregnancies have UR, the majority of which are caused by scarred uteri. Today, the diagnostic paradigm is primarily concerned with incidental presentations, which may or may not include silent cases that predispose to future obstetric issues.² Notably, the clinical importance of having complete or incomplete UR in women that are symptomatic remains poorly understood, despite the potential difference in management and outcome.

This study analyzed a cohort of asymptomatic UR which includes both complete and incomplete UR, to address critical knowledge gaps regarding asymptomatic rupture. The analysis compared clinical and demographic characteristics of different UR types and identified specific risk factors for asymptomatic events. Particular attention was paid to the impact of evaluating the completeness of the UR on subsequent reproductive outcomes and to provide important data for parturient counseling and treatment.

Hence, the study aim was to identify factors associated with the development of UR in cases that were fortuitously discovered during pregnancy or delivery in asymptomatic women.

Methods

Study population

This study included asymptomatic pregnant women with incidentally discovered and intraoperatively confirmed complete UR.

The cohort was defined according to the following criteria:

Inclusion criteria

• ▪ Intraoperative or postpartum diagnosis of UR in the absence of any preceding clinical signs or symptoms (e.g., abdominal pain, vaginal bleeding, or signs of fetal distress).

• ▪ Complete and available medical and surgical records.

Exclusion criteria

• ▪ Cases in which UR was suspected preoperatively, before delivery based on clinical symptoms or abnormal findings during labor monitoring

• ▪ Incomplete or missing data.

Definitions

Two types of UR, complete and incomplete, were distinguished based on whether the overlying serosa of the uterus was involved:^10,11

• ▪ A complete UR was defined as a full-thickness disruption involving the entire uterine wall, including the serosa.

• ▪ An incomplete UR was defined as a partial myometrial defect, often contained by the serosa or peritoneum, with no communication with the peritoneal cavity.

A study flowchart detailing case selection and exclusions has been developed (Figure 1).

Figure 1. Flowchart of the study population.

Results

During the study period, a total of 41 cases of silent UR were included.

From 2014 to 2024 (Table 1 and Figure 2), the maternity unit experienced a significant decrease in annual births, falling from 3939 to just 1964. UR cases peaked at 16 in 2017 but decreased afterward, with only one case reported in 2024. Cesarean deliveries reached their highest point in 2018 at 2033 but declined steadily to 1166 by 2024. In contrast, the number of vaginal deliveries remained relatively stable from 2019 onward, varying between 798 and 1043 each year. Asymptomatic UR accounted for an average of 50% of the UR cases over the eleven-year study period. It exhibited a fluctuating pattern, with the highest occurrence in 2017 (14 cases (88%).

Figure 2. Trends in asymptomatic Uterine Rupture (UR) prevalence (2014-2024): proportion of asymptomatic cases among total UR at Charles Nicolle Hospital.

The average age was 33.29 ± 4.9 years (24-44 years). Among the 41 women with silent UR, 51% were classified as having an average socioeconomic status, followed by 32% with a high status, and 17% with a low status. In terms of educational attainment, 49% had completed secondary education, 32% held a university-level degree, and 19% had attained only primary education.

Table 2 presents descriptive statistics for various variables related to the study population including BMI, gravidity, parity, term, interpregnancy interval, and duration of labor.

Clinically, seven women with silent UR (17%) developed hypertension during pregnancy, and four (10%) were diagnosed with gestational diabetes.

Thirty-six (88%) of the study population arrived in active labor. Labor stagnation occurred in 7 individuals (17%).

Regarding the time of UR diagnosis, 40 URs (98%) were diagnosed after delivery, whilst one (2%) was diagnosed during labor.

Table 3 presents UR type (complete or incomplete), maternal and neonatal outcomes.

Discussion

Between 2014 and 2024, the number of deliveries per year at the institution decreased by 53% (from 3939 to 1964), and the number of cesarean sections decreased by 43% (from a peak of 2033 in 2018 to 1166 in 2024).

At the same time, the number of UR cases decreased from 16 in 2017 to 1 in 2024. Of note, there was also a decrease in asymptomatic cases of UR after 2018 (from 14 in 2017 to 1-3 per year) (Figure 2).

This sustained decline is likely multifactorial. Several key factors may have contributed^14–16:

Although the majority of URs occurred in women with previous cesarean sections, rare etiologies such as placenta accreta spectrum, particularly placenta percreta, have been reported even in unscarred uteri.⁶ Awareness of these uncommon causes remains essential.

Other causes of intra-abdominal hemorrhage during pregnancy should be kept in mind, including placental abruption, UR in unscarred uterus, ruptured splenic or hepatic aneurysms.¹⁷ The etiologies of spontaneous hemoperitoneum in pregnancy are rarely established with the spontaneous rupture of proliferative vasculature relates to some unknown risk factors such as endometriosis, adenomyosis and a relevant history of ovarian tumor removal.¹⁸

Our findings showed that 98% of silent URs were diagnosed post-delivery, suggesting a potential role for enhanced antenatal imaging. High-resolution ultrasound and magnetic resonance imaging (MRI) can detect thinning of uterine scars or dehiscence, but their use remains limited in daily practice. Alalaf et al. demonstrated that during the first stage of labor, a lower uterine segment (LUS) thickness ≤ 2.3 mm and myometrial thickness ≤ 1.9 mm are significantly associated with uterine defects including dehiscence.¹⁹ The most recent systematic review and meta-analysis suggests that an LUS > 3.65 mm should be safe for a TOLAC, 2–3.65 mm is probably safe, and <2 mm identifies a patient at higher risk for UR/dehiscence.²⁰

This cohort showed no demographic (age, body mass index, socioeconomic status) or obstetric (quality of antenatal care, gestational diabetes) associations with UR outcomes. However, two new predictors emerged:

Prolonged labor: Labor longer than 220 minutes increased the odds of complete UR by 45 times (OR=45.231, p=0.009), which is consistent with Savukyne et al.,¹⁵ who identified prolonged labor as a major risk factor.

Lower maternal weight: Weight less than 68 kg decreased the odds of incomplete UR (OR=0.033/kg, p=0.039). Several large cohort studies have shown that lower maternal weight is associated with a significantly reduced risk of UR during TOLAC. For example, Cahill et al. reported that women weighing less than 68 kg had a 70% lower risk of UR compared to heavier women (adjusted OR = 0.3; 95% CI: 0.1–0.8), even after adjusting for birth weight.²¹ Similarly, Bujold et al. found that women with a BMI < 25 kg/m² were significantly less likely to experience rupture compared to those with BMI > 30 kg/m², the latter showing a 2.3-fold increased risk (OR = 2.3; 95% CI: 1.4–3.8).²²

Obesity may predispose to rupture through multiple mechanisms: impaired wound healing due to chronic inflammation and proinflammatory cytokines, poor collagen remodeling, and the formation of fibrotic, poorly vascularized scars. In addition, Landon et al. identified obesity (BMI > 30 kg/m²) as an independent risk factor for UR (OR = 2.7; 95% CI: 1.1–6.6), regardless of fetal size.²³ While macrosomia (>4000 g) is also associated with an increased risk of rupture (OR = 2.5; 95% CI: 1.3–4.8 per Jastrow et al.),²⁴ maternal obesity appears to exert an even stronger effect. Grobman et al. found that both variables independently predicted UR, but maternal BMI had a greater impact than neonatal weight in multivariable models.²⁵ Moreover, Chauhan et al. highlighted that maternal obesity contributes to dysfunctional labor patterns, delayed diagnosis due to increased adiposity, and reduced uterine contractility, all of which increase the cumulative risk of scar failure.²⁶

Together, these findings suggest that maternal weight and body composition are key determinants of uterine scar performance during labor and should be included in individualized TOLAC counseling and decision-making.

Gestational age (38.86 weeks vs. 36.85 weeks, p=0.03) and delivery time (306 minutes vs. 143 minutes, p=0.006) were also longer in incomplete UR cases, suggesting that sustained uterine pressure may have led to partial UR.

Monitoring tools also warrant attention:

Although no cases of pulmonary embolism were reported in our series, thromboprophylaxis during and after cesarean delivery is essential, particularly in women experiencing severe hemorrhage.²⁹

Conclusions

This study highlights that UR can occur without clinical signs and may remain undetected until surgical or postpartum evaluation. Among women with silent UR, we identified two independent predictors of complete rupture: prolonged labor duration > 220 minutes and maternal weight < 68 kg. These findings may contribute to improved risk stratification in pregnant women undergoing trial of labor after caesarean.

Ethical considerations

We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines.

The study protocol was approved on 13 February 2025 by the institutional ethics committee of Charles Nicolle Hospital, Tunis, Tunisia before conducting the study (approval number: FWA 00032748- IORG0011243).

Consent to participate

As this was a retrospective study using anonymized data, informed consent was waived.