Induction of labour as a factor in uterine rupture

Introduction

Many specialists consider the use of labor induction to be a risk factor for uterine rupture, especially in patients with a uterine scar due to a previous cesarean section (CS). Currently, methods such as oxytocin, prostaglandins, mechanical dilators, and balloon catheters are widely used for pre-induction and induction of labor. A combination of two methods is also possible. In this study, we examine the risks of uterine rupture during various types of labor induction.

This paper presents a scientific literature review devoted to an important issue, namely, uterine rupture associated with the induction of labor in obstetric practice. Data were analyzed using international and domestic sources (e-Library, MedLine, PubMed) for the period 2005–2025, using the following keywords: “uterine rupture”, “labor induction”, “hemoperitoneum”, and “perinatal mortality”. Of 90 papers reporting uterine rupture associated with induction of labor, 39 articles that met the selection criteria (excluding other risk factors for uterine rupture) were identified.

The safety of labor induction in women with a uterine scar from a previous CS remains controversial. Opponents of labor induction substantiate the high risk of uterine rupture, which is associated with adverse outcomes for both mother and fetus. On the other hand, supporters believe these risks are exaggerated [1,2]. Furthermore, the primary argument for the unnecessary concern surrounding labor induction is the fact that upon careful monitoring of the mother and fetus, timely surgical intervention can prevent serious complications, such as massive blood loss and antepartum and intrapartum fetal death.

In support of the second point of view, we can cite data from the study by Kayani et al. on the outcomes of labor induction in 200 women with a uterine scar from a previous CS, obtained from a third-level institution in Liverpool (UK). Herein, four cases of uterine rupture and a case of scar dehiscence (gaping) were recorded (2.4%). Two infants were born in a state of profound asphyxia, but in all five cases of uterine rupture, the newborns were healthy at the time of discharge from the hospital [3].

Uterine rupture during induction of labor with Misoprostol

Misoprostol is a synthetic analogue of prostaglandin E₁. Initially, misoprostol was approved for the treatment of gastric ulcers, but within a relatively short period of time, its use expanded to include obstetrics. Currently, misoprostol has earned a privileged place in routine obstetric practice in developing countries due to its low cost and ease of administration, despite numerous complications described in the literature, including uterine hyperstimulation, uterine rupture, and fetal asystole [2]. In Russia, the use of misoprostol for labor induction is not permitted.

It should be noted that misoprostol is now widely used for labor induction not only in developing countries. A Danish investigation published in 2019 attested that before 2016, oral misoprostol at a dose of 50 µg 2–3 times daily was the standard practice for labor induction in pregnant women after 37 weeks, and after 2016, its dose amounted to 25 µg up to 8 times daily. Since 2016, misoprostol induction has been performed as an outpatient procedure for healthy women with uncomplicated pregnancies in Denmark. According to the performed analysis, the low-dose misoprostol induction protocol was associated with favorable obstetric outcomes, leading to an increased probability of vaginal delivery but with a higher risk of vacuum extraction. No cases of uterine rupture were identified. Furthermore, the risk of uterine hyperstimulation increased insignificantly, while the risk of meconium staining of amniotic fluid and CS was slightly reduced [4].

Misoprostol is a recognized method for inducing labor. Nevertheless, the method of preparation and the dosage of misoprostol vary significantly between clinics and often do not comply with international recommendations [5,6]. According to the data published in 2021, misoprostol is one of three preferred methods of inducing labor among German midwives, along with castor oil and complementary/alternative methods [5]. Recent critical reviews have led to the discontinuation of misoprostol use in 17% of clinics, primarily in small obstetric/private clinics with fewer than 1,000 births. However, there have been no reported restrictions on the use of misoprostol for labor induction, either among private midwives or in large perinatal centers.

Since Misoprostol was first used, there has been no clinical protocol or recommendation for its administration in the second trimester of pregnancy. The initial dose has generally been 400 µg, repeated every 4–6 hours, up to a maximum value of 1200–1600 µg per day. Some specialists have recommended using misoprostol in combination with oxytocin or mifepristone to enhance its efficacy. In 2007, FIGO experts recommended a clinical protocol outlining doses and regimens for misoprostol use to terminate pregnancy in the second trimester, which included 100–200 µg of intravaginal misoprostol, repeated administration after 6 hours, with a maximum regimen of 4 doses for 24 hours. It was noted that misoprostol should be used with particular caution in pregnant women with a uterine scar [7].

Several recent studies have shown that misoprostol is effective for inducing labor at various doses and routes of administration. Abroad, current clinical guidelines recommend oral misoprostol administration at a dose of 25 µg every 2 hours. A comparative randomized trial published in 2017 revealed that oral misoprostol at a dose of 25 µg every 2 hours was equally effective as titrated misoprostol solution but with a lower incidence of side effects and complications [8].

Currently, intravaginal misoprostol is widely used worldwide with good results for second-trimester pregnancy termination [9]. However, there are many reports of serious complications associated with the use of misoprostol, including uterine ruptures in both patients with uterine scars from previous surgeries and patients with an intact uterus [10, 11].

There are many predictors of uterine rupture, the most important of which are uterine scar, uterine malformation, multifetation, obstetric maneuvers, instrumental extractions, mechanical dystonia, history of uterine curettage, and the use of uterotonics, including misoprostol [2, 3, 12]. Despite these restrictions, many experts believe that vaginal misoprostol is safe and effective for cervical ripening in the third trimester of pregnancy. In most cases, it promotes successful vaginal delivery within 24 hours, without increasing the rate of CS or adversely affecting fetal outcome [13].

In a study by Dorr, conducted in the USA, no significant differences in the duration of labor and its outcome were found between oral and vaginal misoprostol administration in women undergoing labor induction at full-term pregnancy [14]. Concurrently, the results of another study, also conducted in the United States, attested that a group of patients, who were administered misoprostol intravaginally for induction of labor, had a higher percentage of vaginal deliveries, a shorter duration of the stage from the beginning of induction of labor (20.1 versus 22.8 hours, respectively), and a lower proportion of CSs for fetal reasons (3.3 and 9.5%, respectively).

In 2018, researchers from Morocco described a case of uterine rupture that occurred relatively early in pregnancy (early third trimester) in a patient without any identified risk factors for this medical problem, except for the administration of a low dose of misoprostol (only 100 µg) [16]. Labor was induced at 31 weeks of gestation due to severe preeclampsia, pronounced oligohydramnios, and severe fetal growth restriction syndrome (estimated fetal weight was 524 g). According to the 2012 FIGO guidelines, misoprostol was administered vaginally at a dose of 25 µg every 6 hours for 24 hours (4 doses = 100 µg). Six hours after the fourth dose of misoprostol, the patient experienced irregular uterine contractions, and the following morning, namely 24 hours after the fourth dose, regular labor developed. Uterine rupture was suspected due to the ruptured fetal membrane and the moderately blood-stained amniotic fluid. It should be noted that this patient’s clinical presentation was not typical and manifested. Typical clinical manifestations of uterine rupture are usually characterized by vivid manifestations: severe pain in the lower abdomen and pelvis, symptoms of internal bleeding, hemodynamic instability, and progressive deterioration of the general condition up to the development of shock. The patient’s clinical picture in the presented report was “blurred”, with only pain in the lower abdomen and minor bloody discharge from the genital tract noted. This was explained by the fact that the uterine rupture was accompanied by the formation of a hematoma, while the broad uterine ligament played a compression role, preventing further spread of the hematoma and its diffusion into the abdominal cavity.

There is no doubt that induction of labor with misoprostol increases the risk of uterine rupture in women with a history of CS. In particular, according to a retrospective study conducted in Turkey, uterine rupture occurred in 4 of 41 patients (9.7%) with a uterine scar from a previous CS, in whom labor was induced with misoprostol [17]. Meanwhile, data from a comparative study conducted in the USA showed that the risks associated with induction of labor with misoprostol in patients with a uterine scar after CS were no higher than in the group of women with induction of labor by oxytocin [18].

Uterine rupture during induction of labor with oxytocin

Our literature review showed that not all induction methods had the same risk of uterine rupture, and only a small number of randomized controlled trials have been conducted to assess the outcomes of labor induction in women with a uterine scar from a previous CS. Thus, a study conducted in Israel found that the lowest rate of uterine rupture was in women with a uterine scar from a previous CS upon oxytocin induction, namely 1.1%, compared to 2% with dinoprostone induction and 6% with misoprostol induction [19].

A number of authors point to an increased risk of uterine rupture in women with a uterine scar after a CS during labor induction with oxytocin [20]. For instance, according to Gobillot et al., maternal morbidity rates, especially the incidence of uterine rupture, were higher in women with a previous single CS during labor induction with oxytocin than in women with a similar history who underwent CS. Thus, the incidence of uterine rupture during labor induction with oxytocin was 3.2% (8 cases out of 248 births) [20].

A meta-analysis of all currently available observational studies, published in 2021, revealed that women with a uterine scar from a previous CS and induced labor had a higher risk of uterine rupture compared to women with spontaneous labor. The integrated rates of uterine rupture in women who used oxytocin and women who did not use oxytocin in the group of pregnant women with a uterine scar associated to a CS were 1.4% and 0.5%, respectively, and the difference was significant. The use of oxytocin presumably increases this risk, which may be affected by the induction process or the individual condition of the cervix. According to studies, the incidence of uterine rupture in women undergoing induced labor was slightly higher than in those undergoing spontaneous labor (2.2% versus 0.7%). The authors conclude that a simplified and standardized management of vaginal births, as well as a precise protocol and careful monitoring of oxytocin administration in pregnant women with a uterine scar following a CS, are necessary for a successful outcome [21].

There are contradictory data regarding the impact of oxytocin dose, administration rate, and induction duration on the incidence and risk of uterine rupture. For example, some experts reported no significant differences between the initial oxytocin dose, maximum dose, and time to reach the maximum dose in cases of uterine rupture during labor compared to successful vaginal deliveries in women with a uterine scar following a CS. Other experts, on the contrary, believe that the administration regimen and the dose of oxytocin influence the risk of uterine rupture in women with a uterine scar after a CS. For example, the results of a retrospective multicenter cohort study, which analyzed the relationship between the maximum dose of oxytocin and uterine rupture, showed that using a maximum oxytocin dose of 20 ml/min for labor induction makes it possible to avoid a high risk of uterine rupture. Increasing the maximum oxytocin dose above 20 ml/min was associated with a fourfold or greater increase in the risk of uterine rupture [22, 23].

According to Russian clinical guidelines (Failed Attempt at Labor Induction (Cervical Preparation for Labor and Labor Induction)), approved by the Russian Ministry of Health in 2021, the uterine scar after a CS is not a contraindication for labor induction with oxytocin[1]. They recommend that, if there is a scar on the uterus after a CS, a history of vaginal delivery should be considered as a factor increasing the probability of a successful outcome of labor induction¹.

According to the recommendations presented in the clinical protocol (Postoperative Uterine Scar Requiring Maternal Medical Care During Pregnancy, Childbirth, and the Postpartum Period), approved in 2021, labor induction is not contraindicated in pregnant women with a uterine scar following a CS[2]. The decision on the indispensability for labor induction is recommended to be made based on a partogram after obtaining written consent from the woman in labor and to be carried out exclusively by intravenous administration of oxytocin at a dose not exceeding 20 mIU/min (Level of recommendation: B; Level of evidence: 3). Careful monitoring of oxytocin infusion is recommended to provide a rhythm, which does not exceed 4 contractions in 10 minutes with duration of 45 to 60 seconds each, to ensure the efficacy and safety of labor induction. It is recommended to reconsider labor management tactics toward CS if the woman refuses induction due to appearance of signs of impending uterine rupture, a clinically contracted pelvis, or weak labor that does not respond to treatment within two hours (Level of Recommendation: C; Level of Evidence: 5). In this case, a CS should be initiated as soon as possible but no later than 30 minutes after the decision is made².

Uterine rupture during induction of labor with a balloon catheter

One of the methods of inducing labor in women with one previous CS in their history and an “immature” cervix is the use of a balloon catheter. There are a fairly large number of publications in the databases concerning the efficacy and safety of this induction method in pregnant women with a uterine scar from a previous CS. Some specialists even consider the use of balloon catheters for inducing labor in women with a uterine scar from a previous CS during full-term pregnancy as an alternative to a planned CS [24–26].

A comparative study conducted in France over three years included 101 women who underwent induction of labor using balloon catheterization and 103 women who underwent induction using oxytocin. The vaginal delivery rate was 50% in the balloon catheter group and only 37% in the oxytocin group. Rates of maternal and neonatal morbidity did not differ between the groups. No cases of uterine rupture were reported. Thus, when used for induction of labor in women with a previous CS, a balloon catheter tended to be associated with a higher Bishop cervical score and a higher probability of vaginal delivery compared with low-dose intravenous oxytocin [27].

Swiss specialists came to completely opposite conclusions, showing that the success rate of vaginal birth in women in labor with a uterine scar after a CS upon induction by a Foley catheter was 45.8%, while upon induction using oxytocin it was 63.9%. The results of this study further confirmed the fact that a history of previous vaginal delivery is an independent, favorable prognostic factor for successful vaginal delivery in both groups of patients, regardless of the induction method (balloon catheter or oxytocin). The authors concluded that induction of labor using a balloon catheter in women with a previous CS and an immature cervix has a disappointingly low success rate compared to oxytocin [28].

Jozwiak et al. believe that induction of labor using a transcervical Foley catheter is an effective method for achieving vaginal delivery in women with a previous CS. Furthermore, there is a low risk of uterine rupture and maternal and neonatal (infectious) morbidity in this cohort of patients. The authors reached this conclusion based on an analysis of 2,008 deliveries in women with a uterine scar following CS who underwent induction of labor using a Foley catheter during a subsequent pregnancy. The authors report spontaneous vaginal deliveries in 60% of cases including vacuum extraction used in 11% of cases. Uterine rupture occurred in one woman. Postpartum hemorrhage was the most common complication, accounting for 12%. Intrauterine and postpartum maternal infections occurred in 5% and 1% of cases, respectively. Besides, two cases of perinatal mortality (1%) were recorded, one of which was associated with uterine rupture [29].

A large prospective cohort study, which included data on the outcomes of delivery in women with a uterine scar from a previous CS and a singleton pregnancy in the cephalic presentation of the fetus from 51 hospitals in the Netherlands, compared obstetric and perinatal complications of the use of a Foley balloon catheter and planned delivery by CS. Of the 993 women who underwent induction using a Foley catheter, 560 (56.4%) had a successful vaginal delivery, while 11 (1.1%) experienced uterine rupture [24]. These figures are quite commensurate with the average incidence of uterine rupture in women with a uterine scar after a CS. The overall incidence of obstetric complications, including uterine rupture, severe postpartum hemorrhage, and postpartum infection, was 7.4% in the group of women who underwent induction with a balloon catheter. The overall incidence of these complications in the group of women undergoing a repeat CS was 4.5%. The authors concluded that in women with a previous CS and the demand for vaginal delivery, induction of labor with a balloon catheter does not lead to a significant increase in adverse outcomes for the mother and newborn compared to a planned CS.

In 2019, researchers from the Department of Obstetrics and Gynecology at the University of Washington (Seattle, USA) presented the results of a prospective observational cohort study examining the safety of transcervical Foley catheter insertion for cervical ripening in women with a uterine scar from a previous CS. The authors’ primary objective was to assess whether the use of a Foley catheter during trial of labor in women with a uterine scar following a CS is associated with a risk of uterine rupture. The study’s endpoint was the incidence of uterine rupture. The authors conclude that the Foley catheter is a safe instrument for mechanical dilation in women who have undergone induction of labor following a previous CS [30].

In recent years, a new modification of balloon catheters has emerged that, unlike the Foley catheter, is specifically designed for labor induction. These are double-balloon catheters. The first study examining the efficacy of using a double-balloon catheter for labor induction in Chinese women with a previous CS was presented in 2015. Using a double-balloon catheter, the authors achieved vaginal delivery in women with a uterine scar from a CS in 75% of cases. No serious complications, including uterine rupture, were observed [31]. Concurrently, French specialists, based on an analysis of their own data, showed that the procedure of induction of labor in women, whose cervical condition score according to the Bishop scale was < 5 points, was not without an increased probability of maternal and neonatal risk. The overall frequency of vaginal births upon using a balloon catheter for induction was the lowest and amounted to 50.8%, while after spontaneous development of labor it was 79.1%, and after induction of labor with oxytocin the rate reached 68.2%. Severe forms of maternal and neonatal pathology were observed in 17% and 13.6% of cases, respectively [32].

In 2022, German experts presented an updated review based on the latest evidence [26]. According to current recommendations, intracervical administration of prostaglandin E₂ is associated with a higher rate of uterine rupture compared with the use of balloon catheters. Therefore, balloon catheters are a suitable alternative to prostaglandin E₂ for the induction of labor after a previous CS, even though this use is unofficial. According to a recent meta-analysis, the average vaginal delivery rate after the use of balloon catheters in women after a previous CS is approximately 53%, and the average rate of vaginal deliveries with spontaneous onset of labor is 72%. The uterine rupture rate was 0.2–0.9% with vaginal prostaglandin E₂ and 0.56–0.94% with balloon catheters, which is comparable to the uterine rupture rate associated with spontaneous onset of labor. Furthermore, the authors emphasize that uterine rupture after balloon catheter placement typically occurs not during the period of cervical ripening but rather during the intravenous administration of oxytocin, if used.

In the context of the abovementioned data, obstetricians and gynecologists should pay attention to a number of key points. There is no doubt that pregnant women and women in labor with a uterine scar from a previous CS are at increased risk of uterine rupture. In this category of women, induction of labor may be required when planning and managing a vaginal birth. However, it is unclear which induction method is preferable in terms of safety and minimizing adverse outcomes, including uterine rupture. Therefore, the conclusions of the latest Cochrane review [33] on this issue are relevant: “Data from RCTs on methods of induction of labor in women with a previous CS are insufficient, and the studies available to date do not allow us to identify clinically significant differences in various parameters. The level of assessment of the quality of evidence was moderate to very low due to imprecision and limitations in the study design. Observational studies (cohort studies), including various methods used for cervical ripening, may be a better alternative. High-quality, well-powered randomised clinical trials are unlikely to be conducted due to the very large numbers of cases required to study the risk of uncommon but serious adverse outcomes (e.g., uterine rupture)”.

Conclusions

Thus, there are currently no relevant, evidence-based recommendations on the preferred method of induction of labor in women with a uterine scar from a previous CS, especially for patients with an immature cervix, due to the lack of randomized controlled trials [34–37]. Cervical dilators are currently the only method that is not contraindicated for cervical ripening/labor induction in women who have undergone CS. Intravenous oxytocin and misoprostol are contraindicated in these women due to the high risk of uterine rupture. In women with a mature cervix (Bishop score > 6), intravenous oxytocin is an effective procedure with a commensurate risk of uterine rupture compared to spontaneous labor. The efficacy, benefits, and safety of various labor induction methods are of particular interest to practicing obstetricians. The extensive data currently available in the literature are not always unambiguous and are sometimes contradictory.