Uterine rupture (UR) is a rare but severe complication of pregnancy, especially occurring in women with a history of cesarean sections or uterine surgeries [1, 2]. This condition often leads to critical outcomes for maternal and fetal outcomes [1, 2]. The incidence exhibits variability among different demographic cohorts, revealing a markedly increased prevalence among women who have experienced cesarean sections or alternative uterine surgical interventions. According to the World Health Organization (WHO), UR prevalence is reported as 0.053% in community-based studies, while a higher incidence of 0.31% is observed in medical institution-based studies [3]. The primary causes for UR consist of widespread poverty, illiteracy, cultural factors, advanced age, grand multiparity, unskilled delivery, and misuse of uterotonics, particularly in developing countries [4]. Despite significant economic progress, the prevalence of UR during pregnancy in China has not markedly improved over recent years [5].

Accurate UR diagnosis is complicated by symptom heterogeneity and the lack of established predictive criteria [6, 7]. Early and accurate risk assessment is crucial to prevent adverse maternal and neonatal outcomes [7, 8]. Considering these challenges, the incidence of UR and the outcomes for pregnant women and their unborn children vary, influenced by differences in socio-demographic conditions, preparedness, access to skilled midwives, and the efficiency of health systems across regions [9]. Particularly, the cesarean section rate in China has remained high over several decades, with reports indicating rates range from 40% to 60% in most Chinese hospitals. In some hospitals, this rate has exceeded 70% [10]. This cesarean delivery trend contributes to cesarean scar pregnancy (CSP), a unique variant of ectopic pregnancy, where fertilized eggs and trophoblastic cells implant onto the cesarean section scar [11]. It is widely believed that CSP significantly increases the risk of UR [12, 13]. Thus, previous cesarean delivery (CD) is one of the most vital independent risk factors for UR [12].

Despite early investigations into UR risk factors, many studies have yet to effectively control for confounding variables [5, 14, 15]. Furthermore, most current research has centered on evaluating risk factors for cesarean scar pregnancy and UR during a trial of labor. However, it remains ambiguous whether increased risk correlates with rising CD rates [13, 16]. Additionally, the 2019 American College of Obstetricians and Gynecologists (ACOG) guidelines, along with a Chinese expert consensus group, do not mention maternal age or parity effects on UR [17, 18]. Thus, the association between maternal age, parity, previous cesarean section count, and UR risk remains controversial [13, 16]. Ultimately, more studies are necessary to systematically explore risk factors associated with UR.

This study addresses gaps using a retrospective method and propensity score matching (PSM) to rigorously manage confounding factors [19]. The goal is to pinpoint crucial risk factors, thereby advancing risk assessment and informing clinical strategies to lessen UR incidence and improve maternal-neonatal outcomes.

UR is a rare yet severe obstetric complication during pregnancy, frequently leading to significant health risks for mothers and neonates [30]. Although medical research has identified certain risk factors for UR, many studies have not controlled for potential confounding variables [5, 14, 15]. This study utilized PSM to systematically evaluate the risk factors associated with UR, focusing on the correlation between multiple uterine surgeries and the risk of UR. This study aimed to develop more precise perinatal management strategies to reduce the incidence of UR.

This study demonstrated that the UR rate was 0.024% (72/306,336), lower than previously documented rates (range, 0.13%–0.31%) [3, 5]. We speculate that this discrepancy could be due to differences across distinct geographical regions or normative prenatal examinations. The prevalence of UR during pregnancy continues to increase in China, consistent with the finding reported by Zhou et al. [5]. This study observed UR rates from 2019 to 2023 recorded at 0.0092% (2019), 0.0087% (2020), 0.0349% (2021), 0.0332% (2022), and 0.0368% (2023), respectively.

After PSM matching, this study identified that pregnant women with a history of cesarean section exhibited a significantly increased risk of UR compared to those without such a history. However, multivariate analysis indicated no statistically significant difference between the UR and non-UR groups in cesarean section history. This finding may be due to the inclusion of cesarean section counts in the number of uterine surgeries, which was controlled for in the multivariable model, potentially suggesting that a history of cesarean section could serve as a protective factor. This correlation is particularly relevant, as CSP rates will continue to increase with the rising incidence of cesarean sections [31]. Furthermore, a previous study has demonstrated that women with a previous cesarean section who undergo labor induction with uterotonic drugs are at an elevated risk of UR and subsequent complications [32]. Our study corroborates these findings, revealing that a history of cesarean section significantly increases the risk of UR and estimated blood loss during delivery. Specifically, we found that a history of cesarean section significantly increased the risk of UR and estimated blood loss during delivery. However, CSP presents with nonspecific clinical symptoms in early pregnancy or only resembles signs of threatened miscarriage, such as slight vaginal bleeding and mild lower abdominal pain [33]. Critically, the diagnosis of CSP relies on identifying the gestational sac within the uterine scar, as detected by ultrasound or magnetic resonance imaging (MRI) [34]. Nonetheless, owing to the relatively low sensitivity of imaging examinations, many CSP patients may be misdiagnosed. Consequently, such misdiagnosis may result in dilation and curettage procedures for suspected pregnancy failure, leading to severe complications [33].

This study revealed that the incidence of uterine surgeries was significantly higher in the UR group (2.87 $\pm$ 1.65) than in the non-UR group (1.53 $\pm$ 0.67, p 0.001). Subsequent multivariate analysis further substantiated that multiple uterine surgeries constituted an independent risk factor for UR (OR: 3.141; 95% CI: 1.903–5.183; p 0.001). These findings underscore the critical role of identifying and closely monitoring pregnant women with a history of multiple uterine surgeries during perinatal care. This aligns with previous research [12, 13]. Evidence suggests that subsequent abdominal myomectomies can increase UR risk [35]. Similar results were obtained in the present study. We found that the number of uterine surgeries performed significantly increased the risk of UR.

Indeed, the extent of uterine surgery and the surgical modality utilized can affect our findings. However, it is undeniable that less-invasive procedures would likely decrease this risk. Hurst et al. [36] suggested that the existence of any difference, such as surgical technique, instruments, energy devices, or laparotomy, might result in myometrium wound healing difficulties. These include myometrial defects not being fully sutured, hematoma formation, and excessive unipolar or bipolar electrocautery severing blood vessels within the myometrium. These factors are thought to interfere with the healing of myometrial wounds and increase the risk of rupture. Prior studies have been inconsistent, with one finding no relation [37] and several others showing that the hysterectomy rate after UR is associated with scar pregnancy [38, 39, 40]. Researchers have speculated that treatment tends to be delayed because of a low suspicion index in patients without a history of uterine surgery [22]. In addition, unscarred UR most often occurs in the uterine body and outside the uterus. Therefore, surgical repair is a far more significant challenge than scarred UR. It is probably one of the reasons leading to the increase in severe maternal outcomes [37, 38]. Therefore, not following an antenatal care plan may increase hysterectomy rates. Colmorn et al. [41] expressed a similar view that certain hysterectomies can be avoided if UR is adequately repaired early.

In this study, a statistically significant difference was observed between the complete and incomplete UR groups in the distribution of gestational age (p = 0.024). Notably, between 26 and 36 weeks, the incidence of complete UR was markedly higher in the complete rupture group than in the incomplete rupture group (41.18% vs. 13.33%, respectively). This finding indicates a potentially substantial increase in the risk of complete UR during the gestational period. The elevated risk during this gestational period could be attributed to multiple factors. During this phase, uterine growth and fetal development reach a critical peak, and the tension in the uterine wall is markedly heightened, potentially elevating the risk of UR [7]. Moreover, the increase in fetal weight and amniotic fluid volume could impose additional stress on the uterine wall, which may explain the higher prevalence of complete UR observed at this stage of gestation [32, 42]. Therefore, clinicians should conduct more rigorous surveillance and management of these high-risk pregnancies during the 26–36-week gestational period to promptly detect and address potential UR risks.

Our study is subject to several limitations. Firstly, the data were obtained from a relatively small patient sample, and we lacked comprehensive pregnant women’s information regarding the location, quantity, onset, symptoms, and outcomes of the ruptures. These diverse rupture characteristics could substantially impact both fetal and maternal outcomes. Secondly, we could not collect sufficient data on the extent of uterine surgery and the surgical modalities employed in patients with a history of uterine surgery. Thirdly, the study was conducted in a region characterized by advanced economic development in China, with participating hospitals of higher rank (comprising seven third-level hospitals and four second-level hospitals), which may have influenced the study outcomes. Fourthly, although PSM effectively reduced certain biases, several unaddressed confounding factors, such as the socioeconomic status of pregnant women, access to prenatal care, and the experience and qualifications of the surgical team, may affect the incidence of UR. Fifthly, concerning neonatal outcomes, our data collection remains incomplete, with specific complications arising from UR necessitating further data collection and statistical analysis to achieve a comprehensive assessment. Therefore, the UR rates in this study should be analyzed cautiously.

In future research endeavors, we aim to broaden the scope of our study by incorporating additional regions, larger datasets, and comprehensive data collection methodologies. We will employ advanced statistical techniques to account for confounding variables. Our analysis will include detailed information on variables such as location, frequency, onset characteristics, symptoms, rupture outcomes, administration of uterotonics, presence of fetal macrosomia, and types of uterine surgeries. Special emphasis will be placed on examining the impact of the type and frequency of uterine surgeries on the risk of UR.

The study found that multiple uterine surgeries significantly increased the risk of UR during pregnancy, highlighting the need for a thorough obstetric history. It emphasizes the importance of targeted perinatal management, especially in areas with increasing cesarean rates. Health authorities should work to prevent UR by ensuring proper use of partographs and avoiding unnecessary cesareans.

The data used or analyzed during the current study are available from the corresponding author upon reasonable request.

XX, YX, and WS were involved in protocol development, data analysis, and manuscript writing. XX and WS were involved in data management and analysis. XX, YX, YS, and WS were involved in protocol development and responsible for reviewing the data. XX and YX were involved in project development, data collection, and manuscript editing. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.

All procedures followed the ethical standards of the responsible committee on human experimentation (institutional and national) and the 1975 Helsinki Declaration (in its most recently amended version). The study was approved by the Ethical Committee of the Wuxi Maternity and Child Health Hospital (reference number: 2020-01-07-0731-23). As this was a retrospective study, the requirement for informed consent was waived by the ethics committee.

We thank the ultrasonologist Jinxiao Sun in the ultrasound department, Taihu Sanatorium of Jiangsu Province, for reviewing the uterine ultrasound images.

This study was supported by a grant from the Jiangsu Provincial Key Discipline of Maternal and Child Health (No. SFY3-JS2021), and Scientific Research Project of the Health and Family Planning Commission of Wuxi City (No. M202057), Scientific Research Project of Wuxi Health and Family Planning Commission (No. FYKY202303).

The authors declare no conflict of interest.