Analysis of the uterine rupture during pregnancy and delivery in a provincial maternal and children care hospital in China: 2013-2022.

The medical records of all deliveries at Hunan Maternal and Child Health Hospital from January 2013 and December 2022 were retrieved from the hospital database and reviewed. All cases of women with uterine rupture were included. Our hospital is a tertiary referral center for critical and severe diseases of pregnant and delivery women and has an average of 15,000 births per year in Hunan Province, and no changes in general policies with respect to referral, hospitalization, or the transfer of patients from other hospitals have occurred in the last 10 years. This study was approved by the ethics committee of our hospital (2020S072). All patient data were de-identified. The clinical characteristics of each patient with uterine rupture were collected and analyzed, including demographics, obstetric history(previous pregnancy, history of previous surgery), maternal complications, situation at the time of uterine rupture (rupture site and length, the diagnosis of uterine rupture), clinical characteristics, maternal and infant outcomes (hemorrhagic shock, postpartum hemorrhage, hysterectomy, uterine repair surgery, neonatal intensive admission, perinatal asphyxia, birth weight). The 28-week point is the demarcation line between mid-pregnancy and late pregnancy. Stillbirths and perinatal deaths also use this 28-week mark as a cut-off. In China, the 28th week of pregnancy holds particular significance because it is considered a critical point for fetal viability. Although modern medical technology has made it possible for babies born earlier to survive, those born at 28 weeks generally require less medical intervention and support. Government and medical institutions use this timeline to formulate relevant medical policies and educate pregnant women about the importance of prenatal care. According to the gestational age at which a pregnant woman experiences uterine rupture, two groups are formed based on the 28-week mark. In addition, we compared pregnant women with uterine rupture who exhibit symptoms such as abdominal pain or vaginal bleeding to those without these symptoms. The 9th edition of Obstetrics and Gynecology defined uterine rupture as a rupture of the body or lower portion of the uterus. Two types of uterine rupture, complete and incomplete, were distinguished based on whether the overlying serosa of the uterus was involved [ 10 ]. Pregnancy in the middle or second trimester generally lasts from the 13th to the 27th week. The third trimester of pregnancy referred to the final stage, starting from the 28th week and continuing until just before childbirth [ 10 ]. 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 [ 10 ]. Fetal macrosomia was defined as a newborn weighing more than 4,000 g within one hour of birth [ 10 ].China’s two-child policy, effective from 2016, enables couples to have two children. Massive transfusion is defined as the administration of red blood cells totaling 1000 milliliters or more (equivalent to 5 units) during treatment. The diagnostic codes for uterine rupture were O71.0 and 071.1, based on the 10th revision of the International Classification of Diseases (ICD) [ 11 ]. Data were analyzed using the SAS package (version 9.4). Continuous variables were summarized by the mean ± SD or the medians and interquartile range (IQR). Frequencies are presented as percentages. The Student t-test was used for continuous variables and the χ 2 test or Fisher exact test were used for categorical variables. The Wilcoxon test was performed for non-normally distributed data. The level of significance was set at P  < 0.05.Multivariate logistic regression was used to hand confounding factors in the comparison between groups.

There were 153,722 deliveries in total during the study period, 129 patients suffered uterine rupture, conferring an incidence of 8.4/10,000.There were 12 cases with an incidence of 0.78 /10,000 in the second trimester, and 117 cases with an incidence of 7.61 /10,000 in the third trimester. Among them, there were 8 cases with complete rupture and 121 cases with incomplete rupture. (Fig.  1 ). Fig. 1 Flow diagram of patients included in the analysis Flow diagram of patients included in the analysis The median maternal age at rupture was 33 years (22–47 years).The median gestational age at diagnosis of uterine rupture was 38 weeks (15–41 weeks). Among them, 87 cases were diagnosed at ≥ 37 weeks of gestation, 42 cases were diagnosed at < 37 weeks of gestation. Their median gravidity was 3(1–9), and the median number of births was 1(0–4). The median interval from last cesarean section was 5 years, ranging from 1 to 14 years. Most of them had a history of cesarean section (73.6%). 59.7% of cases had a history of dilation and curettage. Twenty-seven (20.9%) cases underwent a labor trial, and 11.6% had received oxytocin. The median diameter of the rupture was 4 cm, with a range of 1 to 12 cm. Of the 129 cases, most (82.2%) were confirmed visually during surgery, whereas the rest (17.8%) were diagnosed using ultrasonography. The rupture was more likely to occur on the lower uterine segment(86.82%)and the uterine fundus or cornua uteri (13.18%). (Table  1 ). Table 1 The general characteristics of the participants General characteristics Median / n Range/ % Maternal age(years) 33 a 22–47 Gestational age at diagnosis of uterine rupture (weeks) 38 a 15–41 Gravidity 3 a 1–9 Number of deliveries 1 a 0–4 Length of rupture(cm) 4 a 1–12 Interval from last CS (years) 5 a 1–14 Previous cesarean section 95 73.6% Trial of labor 27 20.9% Use of oxytocin 15 11.6% A history of dilation and curettage 77 59.7% The diagnosis of uterine rupture  Visually confirmed during surgery 106 82.2%  Ultrasonography 23 17.8% Site of rupture  Lower segment 112 86.8%  Uterine fundus or cornua uteri 17 13.2% Abbreviation: a we applied the median to describe gestational age The general characteristics of the participants Gestational age at diagnosis of uterine rupture (weeks) Abbreviation: a we applied the median to describe gestational age Among the 129 pregnant women, five (3.88%) underwent hysterectomy, including four who had total hysterectomy and one who had subtotal hysterectomy. Bladder repair surgery was performed on five cases (3.88%), and 17 cases (13.18%) required blood transfusion, of which 10 cases (7.75%) received massive transfusions. Among the 129 pregnant women, 25 (19.38%) experienced postpartum hemorrhage, 9 (6.98%) went into shock, and there was one case of maternal death due to uterine rupture. According to the trimester in which the uterine rupture happened, the 129 cases were grouped into two categories based on the 28-week mark. Women with second-trimester uterine rupture were more likely to have undergone a TOLAC (50% versus 11.49%; P  = 0.015) and receive oxytocin (33.33% versus 9.40%; P  = 0.047) (Table  2 ). The multivariable logistic regression model identified both TOLAC (adjusted OR = 4.76, 95% CI 1.09-20.86; P  = 0.038) and placenta accreta (adjusted OR = 6.13, 95% CI 1.23-30.48; P  = 0.027) as independent risk factors for uterine rupture when compared to cases occurring after 28 weeks of gestation. (Table  3 ).Table  4 univariate analysis reveals that patients with uterine rupture during mid-trimester had a higher postpartum hemorrhage occurrence (50% versus 16.24%; P  = 0.015), and subsequently were more likely to receive a blood transfusion (41.67% versus 10.26%; P  = 0.009). Women with second-trimester uterine rupture were more likely to undergo hysterectomy (25% versus 1.71%; P  = 0.006) and exhibited higher rates of bladder injury (33.33% versus 0.85%; P  < 0.001), along with longer hospital stays ( P  = 0.000). After adjusting for potential confounders, logistic regression demonstrated strong associations between mid-trimester uterine rupture and two surgical interventions: blood transfusion (adjusted OR =19.92, 95% CI 4.29-92.45; P  = 0.000) and bladder repair (adjusted OR =21.03, 95% CI 1.31-337.42; P  = 0.032 (Table  5 ). Table 2 The comparison of clinical characteristics of deliveries divided by 28 weeks characteristics < 28 weeks a ( n  = 12,%) ≥ 28 weeks a ( n  = 117,%) P -value Age, y(median, IQR) 31.0(29.0-33.5) 33.0(30.0–36.0) 0.177 b Gravidity(median, IQR) 3(2–4) 3(2–4) 0.401 b Number of deliveries 0.689  0 2/12(16.67%) 10/117(8.55%)  ≥ 1 10/12(83.33%) 107/117(91.45%) Dilation and curettage 1.000  ≥ 1 7/12(58.33%) 70/117(59.83%) Multiple pregnancy 2/12(16.67%) 9/117(7.69%) 0.605 IVF-ET 2/12(16.67%) 16/117(13.68%) 1.000 Uterine malformation 1/12(8.33%) 2/117(1.71%) 0.256 Previous myomectomy 1/12(8.33%) 4/117(3.42%) 0.956 Placenta accreta 3/12(25.00%) 8/117(6.84%) 0.109 Previous Cesarean section 8/12(66.67%) 87/117(74.36%) 0.817 TOLAC 4/8(50.00%) 10/87(11.49%) 0.015 Protracted descent 0/12(0.00%) 3/117(2.56%) 1.000 Use of oxytocin 4/12(33.33%) 11/117(9.40%) 0.047 Previous tubal surgery for ectopic tubal pregnancy 2/12(16.67%) 15/117(12.82%) 1.000 Uterine rupture 0.162  Complete UR 2/12(16.67%) 6/117(5.13%)  Incomplete UR 10/12(83.33%) 111/117(94.87%) Site of rupture 1.000  Lower segment 10/12(83.33%) 102/117(87.18%)  Uterine fundus or cornua uteri 2/12(16.67%) 15/117(12.82%) Clinical manifestations 0.6393  Abdominal pain 4/6(66.67%) 49/65(75.38%)  Vaginal bleeding or other manifestations 2/6(33.33%) 16/65(24.62%) Note: Data were expressed as median (IQR) or n (%) and p values for statistical significance. Abbreviation: a <28 weeks: gestational week at the time of uterine rupture less than 28 weeks, ≥ 28 weeks: gestational week at the time of uterine rupture at least 28 week, b The Wilcoxon test was used. CS: cesarean section, UR: uterine rupture, TOLAC: trial of labor after cesarean, IVF-ET: in vitro fertilization and embryo transfer The comparison of clinical characteristics of deliveries divided by 28 weeks Uterine fundus or cornua uteri Vaginal bleeding or other manifestations Note: Data were expressed as median (IQR) or n (%) and p values for statistical significance. Abbreviation: a <28 weeks: gestational week at the time of uterine rupture less than 28 weeks, ≥ 28 weeks: gestational week at the time of uterine rupture at least 28 week, b The Wilcoxon test was used. CS: cesarean section, UR: uterine rupture, TOLAC: trial of labor after cesarean, IVF-ET: in vitro fertilization and embryo transfer Table 3 Multivariable logistic regression analysis of clinical characteristics of uterine rupture divided by 28 weeks characteristic β (SE) Wald χ² p -value OR (95% CI) Oxytocin 1.4548 (0.7495) 3.77 0.052 4.28 (0.99–18.61) TOLAC 1.5609 (0.7534) 4.29 0.038 4.76 (1.09–20.86) Placenta 1.8137 (0.8181) 4.91 0.027 6.13 (1.23–30.48) Multivariable logistic regression analysis of clinical characteristics of uterine rupture divided by 28 weeks Table 4 The comparisons of maternal complications of deliveries divided by 28 weeks Complications < 28 weeks a ( n  = 12,%) ≥ 28 weeks a ( n  = 117,%) P -value Preoperative diagnosis 4/12(33.33%) 19/117(16.24%) 0.281 Maternal death 0/12(0.00%) 1/117(0.85%) 1.000 Hemorrhagic shock 2/12(16.67%) 7/117(5.96%) 0.198 Postpartum hemorrhage 6/12(50.00%) 19/117(16.24%) 0.015 Blood transfusion 5/12(41.67%) 12/117(10.26%) 0.009 Massive blood transfusion 4/12(33.33%) 6/117(5.13%) 0.004 Hysterectomy 3/12(25.00%) 2/117(1.71%) 0.006 Repair of ruptured bladder 4/12(33.33%) 1/117(0.85%)  5 11/12(91.67%) 61/117(52.14%) 0.009 Intensive care 3/12(25.00%) 10/117(8.55%) 0.194 Note: Data were expressed as median (IQR) or n (%) and p values for statistical significance Abbreviation: a <28 weeks: gestational week at the time of uterine rupture less than 28 weeks, ≥ 28 weeks: gestational week at the time of uterine rupture at least 28 weeks. b The Wilcoxon test was used The comparisons of maternal complications of deliveries divided by 28 weeks Note: Data were expressed as median (IQR) or n (%) and p values for statistical significance Abbreviation: a <28 weeks: gestational week at the time of uterine rupture less than 28 weeks, ≥ 28 weeks: gestational week at the time of uterine rupture at least 28 weeks. b The Wilcoxon test was used Table 5 Multivariable logistic regression analysis of maternal complications of uterine rupture divided by 28 weeks Variable β (SE) Wald χ² p -value OR (95% CI) Blood transfusion 2.9918 (0.7831) 14.60 0.000 19.92 (4.29–92.45) Bladder injury 3.0458 (1.4161) 4.63 0.032 21.03 (1.31–337.42) Multivariable logistic regression analysis of maternal complications of uterine rupture divided by 28 weeks Among the 129 cases of uterine rupture, there were 139 fetuses. Of the 139 fetuses, maternal uterine rupture occurred due to intrauterine fetal demise or planned induction of labor in 16 cases, including one twin pregnancy (12.23%, 17/139).Among the 122 live-born infants, five experienced neonatal asphyxia, and 29 were transferred to the neonatal ICU. When uterine rupture occurs before 28 weeks, it is clear that the outcome of the newborn must be poor, regardless of the state of the rupture. See Table  6 . Table 6 The comparisons of neonatal complications of deliveries divided by 28 weeks Complications < 28weeks a ( n  = 12,%) ≥ 28weeks a ( n  = 117, %) Fetal outcome  survival 3/14(21.43%) 119/125(95.20%)  Stillbirth 11/14(78.57%) 6/125(4.80%) Fetal anomaly 2/14(14.29%) 4/125(3.20%) Fetal macrosomia 0/14(0.00%) 5/125(4.00%) Premature infant 3/3(100%) 35/119(29.41%) Neonatal intensive care 3/3(100%) 26/119(21.85%) Neonatal asphyxia 0/3(0.00%) 5/119(4.20%) Note: Data were expressed as n (%) and p values for statistical significance. Abbreviation: a <28 weeks: gestational week at the time of uterine rupture less than 28 weeks, ≥ 28 weeks: gestational week at the time of uterine rupture at least 28 weeks The comparisons of neonatal complications of deliveries divided by 28 weeks Note: Data were expressed as n (%) and p values for statistical significance. Abbreviation: a <28 weeks: gestational week at the time of uterine rupture less than 28 weeks, ≥ 28 weeks: gestational week at the time of uterine rupture at least 28 weeks Twelve ruptures occurred in the second trimester. They resulted in eleven perinatal deaths (all stillbirths) and three hysterectomies, but no maternal deaths. Eight had a history of prior cesarean section (five of them had previous curettage, three of them were associated with abnormally invasive placenta), accounting for 66.67% of the cases. Seven (58.33%) had previous curettage. There were five instances of uterine rupture requiring transfusions, including four that needed significant amounts of blood. Three of these cases resulted in a total hysterectomy, and unfortunately, four associated fetuses did not survive. The first woman had two previous tubal surgeries due to ectopic pregnancies, one CS and one curettage. She underwent induced labor with ethacridine and misoprostol, resulting in the vaginal delivery of a stillbirth. This was accompanied by abdominal pain and shock. Ultrasound examination revealed hemoperitoneum. Due to a large uterine rupture and extensive placenta accreta with penetrating implantation, an emergency total hysterectomy was performed. The blood loss amounted to 2400 ml, and the site of uterine rupture was located at the scar from a previous cesarean section. The second woman had one vaginal delivery, one CS and five curettages. She presented with persistent abdominal pain, and an ultrasound showed uterine rupture. A cesarean section was performed, delivering a stillbirth. During surgery, it was observed that there was a large area of missing myometrium in the lower segment of the anterior uterine wall. The placenta was found to be implanted deeply, penetrating both the uterus and the posterior wall of the bladder. Postpartum hemorrhage amounted to 4000 ml. Consequently, a total hysterectomy and bladder repair were performed. The third woman had one curettage and one CS (fetal distress, hemorrhage1200, erythrocyte 4U). She underwent induced labor with ethacridine and mifepristone, and ended with a cesarean section of a stillbirth. During the surgery, a large number of engorged vessels were observed on the surface of the uterus, and postpartum hemorrhage amounted to 1500 ml. A total hysterectomy and bladder repair were performed. The site of uterine rupture was located at the scar from the previous cesarean section. The fourth woman had two previous tubal surgeries due to ectopic pregnancies. She experienced lower abdominal distension and pain for 12 h and vaginal bleeding for 1 h before being admitted to the hospital. The fetal heartbeat was undetectable; an emergency cesarean section was performed, resulting in the delivery of a stillborn baby. Postpartum hemorrhage amounted to 2020 ml. The rupture was in the uterine horn associated with prior tubectomy. The fifth woman had a history of denomyosis hysteroscopic treatment. She presented with abdominal pain, and an ultrasound showed uterine rupture. A cesarean section was performed; delivering an infant (700 g). She experienced postpartum hemorrhage totaling 4000 milliliters, accompanied by hemorrhagic shock and presented with fundal rupture associated with placenta accreta. (See Table  7 ). Table 7 Basic information, diagnosis, treatment and pregnancy outcome of 5 patients with blood transfusion in the < 28 week group Serial number Age(y) Gestation week(w) Pregnancy/parity( n ) Risk factor Surgical method Bleeding volume(ml) and blood transfusions Location and size of the breach Clinical manifestations Outcome 1 31 25 + 2 5/1 CS1, AA1, 2013 LaparoscopicRightTubectomy,2003 LaparoscopicTubal Opening and Embryo Extraction, placenta accreta TH Intraperitoneal 1000, hemorrhage1400 erythrocyte 8U, plasma 200 ml, cold precipitation 1U Original CS scar,6 cm, the anterior uterine wall, 10 cm Lower abdominal pain, (after VB)cyanosis of the mouth and lips, pale face, ultrasound: shows uterine rupture Stillbirth, Cleft lip and palate 2 47 27 + 3 8/2 AA5,CS1,VB1, placenta accreta HD + TH + BR Intraperitoneal 600, hemorrhage3200,erythrocyte7U, plasma350ml the anterior uterine wall,8 cm persistent abdominal pain 6 h, ultrasound: shows uterine rupture Stillbirth 3 36 20 + 3 3/1 AA1,CS1(2012Fetal distress, hemorrhage 1200, erythrocyte 4U) HD + TH + BR Intraperitoneal1000, hemorrhage1500 erythrocyte 10U, plasma 400 ml, cold precipitation 2U Original CS scar, lower part of the uterine wall,8 cm Stillbirth, Cleft lip and palate 4 33 23 + 6 3/0 2019Laparoscopic Right Tubectomy,2020Laparoscopic LeftTubal Opening and Embryo Extraction, HD + UR Intraperitoneal 400, hemorrhage1620,erythrocyte4U, plasma400ml, autologous blood 539 Uterine horn extends toward the fundus, 8 cm, the placenta is in the abdominal cavity Lower abdominal pain12h, vaginal bleeding 1 h, fetal heart rate disappears Stillbirth(twins) 5 34 27 + 1 1/1 2020Adenomyosis(HIFU), Hysteroscopic treatment, epileptic, placenta accreta CS + UR Intraperitoneal 600, hemorrhage 3400,erythrocyte13.5U, plasma 700 ml, cold precipitation 14U, autologous blood 1581 upper section of anterior fundal wall,5 cm ultrasound: shows uterine rupture 8’-9’ 700 g, NICU Caesarean Section CS, Artifical Abortion AA, Vaginal Birth VB, Hysterotomy Delivery HD, Total Hysterectomy TH, Uterine Repair UR, Bladder Repair BR, High Intensity Focused Ultrasound HIFU, Neonatal intensive care unit, NICU Basic information, diagnosis, treatment and pregnancy outcome of 5 patients with blood transfusion in the < 28 week group 2020Adenomyosis(HIFU), Hysteroscopic treatment, epileptic, placenta accreta Caesarean Section CS, Artifical Abortion AA, Vaginal Birth VB, Hysterotomy Delivery HD, Total Hysterectomy TH, Uterine Repair UR, Bladder Repair BR, High Intensity Focused Ultrasound HIFU, Neonatal intensive care unit, NICU The study reported the tragic death of a 33-year-old woman in her second pregnancy, occurring at 41 weeks of gestational age. She had one vaginal delivery and a cervical LEEP procedure (a procedure where the cervical cone is excised) before. The patient underwent induced labor with dinoprostone and ultimately ended with an emergency cesarean section due to the stalled descent of the fetal head. She experienced a severe postpartum hemorrhage, with an estimated blood loss of 5600 ml. The newborn was classified as macrosomic (birth weight > 4000 g) and had an Apgar score of 4 at 5 min. Additionally, the patient presented with a fundal rupture measuring 10 centimeters in diameter. She underwent a hysterectomy, and unfortunately, experienced complications such as vomiting and aspiration, which led to low blood oxygen levels and several cardiac arrests. She went into hemorrhagic shock, and ultimately, disseminated intravascular coagulation (DIC) contributed to her death. Our research indicates that the most common clinical symptom is abdominal pain (41%), followed by vaginal bleeding (14%), and 45% of patients with uterine rupture did not present these symptoms. When comparing pregnant women with uterine rupture who have symptoms such as abdominal pain or vaginal bleeding to those without these symptoms, it was found that the group exhibiting clinical symptoms demonstrated a notably higher preoperative diagnosis rate, an increased frequency of neonatal ICU admissions. The differences were statistically significant ( p  = 0.014, 0.005), as detailed in Tables  8 and 9 . Table 8 Comparison of outcomes in pregnant women with uterine rupture with and without abdominal pain or vaginal bleeding Complications Abdominal pain or vaginal bleeding or other manifestations ( n  = 71, %) No manifestation ( n  = 58, %) P -value Preoperative diagnosis 18(25.35%) 5(8.62%) 0.014 Complete UR 5(7.04%) 3(5.17%) 0.730 Hysterectomy 3(4.23%) 2(3.45%) 1.000 Repair of ruptured bladder 3(4.23%) 2(3.45%) 1.000 Massive blood transfusion 6(8.45%) 4(6.90%) 1.000 Postpartum hemorrhage 16(22.54%) 9(15.52%) 0.316 Hemorrhagic shock 5(7.04%) 4(6.90%) 1.000 Comparison of outcomes in pregnant women with uterine rupture with and without abdominal pain or vaginal bleeding Table 9 Neonatal outcomes in pregnant women with uterine rupture with and without abdominal pain or vaginal bleeding Complications Abdominal pain or vaginal bleeding or other manifestations( n  = 71) No manifestation ( n  = 58) Total N N(%) Total N N (%) P-value Stillbirth or neonatal death 77 12(15.58%) 62 5(8.06%) 0.179 Neonatal intensive care 65 22(33.84%) 57 7(12.28%) 0.005 Neonatal asphyxia 65 3(4.62%) 57 2(3.51%) 1.000 Birth weight (median, IQR) 65 3100(2500–3400) 57 3100(2800–3500) 0.235 a Note: Data were expressed as median (IQR) or n (%) and p values for statistical significance. a The Wilcoxon test was used Neonatal outcomes in pregnant women with uterine rupture with and without abdominal pain or vaginal bleeding Note: Data were expressed as median (IQR) or n (%) and p values for statistical significance. a The Wilcoxon test was used We also collected some information about a trial of labor after cesarean delivery (TOLAC). In the study, fourteen women attempted a TOLAC (trial of labor after cesarean). Among them, two cases were found to have uterine rupture after vaginal delivery and underwent uterine repair. In the course of attempting vaginal delivery, 12 patients experienced uterine rupture or encountered emergent issues such as scar tenderness, hematuria, greenish-yellow amniotic fluid, necessitating an immediate cesarean section to conclude childbirth. In the group of women who experienced a second-trimester rupture, those with a previous cesarean section had a high rate of attempting vaginal trial labor ( p  = 0.038).

The present study has several strengths. Firstly, previous studies [ 2 , 45 – 46 ] have been conducted mainly focusing on the differences of uterine rupture between a scarred uterus and an unscarred uterus, or a complete rupture and an incomplete rupture. The study aims to assess the differences of the clinical characteristics and outcomes between the second and third-trimester rupture diagnosed and treated at a single institution with a study period of ten years. Secondly, the strength of this study is that physical hospital records for all patients were reviewed to validate the routinely coded data, ensuring that the definition of uterine rupture was consistent as well as ensuring a high level of accuracy of patient outcome data. However, the current study has several limitations. Because this study is the retrospective design, there could be no control of additional associated factors. The study period spanned 10 years; it was difficult to collect more obstetric indicators, such as minimum hemoglobin level, vaginal secretions. The second limitation is the not-so-big number of cases in our database in a single-center study. Therefore the results may not be applicable to other tertiary hospitals in China. A multicenter study should be performed to confirm our findings.

Uterine Rupture (UR), a complete or partial rupture of the uterine body or lower segment of the uterus during pregnancy or delivery, is a potentially life-threatening condition for both mother and fetus. The primary risk factor for uterine rupture is uterine scar in a previous cesarean delivery [ 1 ]. In addition to caesarean section scar, Other associated risk factors include uterine surgery, placenta accreta, induction of labor(IOL), congenital uterine anomaly, short interval between deliveries [ 2 – 4 ]. A multicenter study of 13 provinces in China showed that the incidence of uterine rupture was 0.03% [ 5 ].Although this incidence rate is low, uterine rupture is highly likely to lead to serious adverse outcomes. Since the full liberalization of the two-child policy in 2016 and the opening of the three-child policy in 2021, the cesarean section rate in China has increased from 43.36% (2017) to 45.00% (2022) [ 6 ]. Concurrently, the proportion of women in China with prior childbirth experience has risen to 53.27% (2022) [ 6 ]. At the same time, the estimated incidence of related pregnancy complications, particularly uterine rupture, is increasing annually [ 7 ]. Previous studies had concentrated more on late-pregnancy uterine rupture in women with prior cesarean sections, while research on mid-trimester uterine rupture was few. Uterine rupture in the second trimester of pregnancy is extremely rare. The literature on uterine rupture during mid-trimester is indeed limited, primarily consisting of case reports and small case series [ 8 – 9 ]. This makes it challenging to draw broad conclusions about the risk factors, presentation, and outcomes associated with this complication. Therefore, in this study, we aimed to analyze the prevalence, clinical characteristics and maternal and neonatal complications of mid-trimester and late-pregnancy uterine rupture and provide practical experience for the early recognition, management and emergency treatment of uterine rupture.

In summary, the second and early third-trimester uterine rupture remains a diagnostic challenge but is associated with catastrophic outcomes. In addition, remarkably worse maternal outcomes were seen in patients with second-trimester rupture when compared with patients who experienced late-pregnancy rupture. Pregnant women with a history of uterine surgery, even at an early gestational age, should be closely monitored by obstetricians for the risk of uterine rupture if they experience persistent abdominal pain. Graded management (all pregnant women need to be risk-graded, well-educated and strict control of high-risk factors), early hospitalization and individualized delivery plans for patients at high risk of uterine rupture are key to the early diagnosis and treatment of uterine rupture. By remaining vigilant about uterine rupture, identifying and managing high-risk pregnant women, and enhancing the emergency treatment capabilities of multidisciplinary medical teams, clinicians can improve maternal and neonatal outcomes.

The incidence of uterine rupture varies between 0.005% and 0.08% in developed countries [ 12 – 16 ], with the tendency of being lower in the developed countries than the developing countries [ 14 , 17 ]. A multicenter study in China showed that the incidence of uterine rupture was 0.03% [ 5 ].The reported incidence of uterine rupture: is 0.0196% in the First Maternity and Infant Hospital of Shanghai [ 18 ], 0.05% in the Women’s Hospital of the Medical College of Zhejiang University [ 19 ], and Yangwen Zhou et al. [ 20 ] study show that the total incidence of uterine rupture in China is 0.13%, close to 0.08% found in our study. All surgical interventions causing damage to the uterine muscular layer during gynecological procedures are considered high-risk factors for uterine rupture during pregnancy. These include myomectomy, interstitial resection of the fallopian tubes, resection of the uterine cornua, hysteroscopic electrotomy, electroablation, dilation and curettage [ 21 ].One source of uterine scarring is caesarean section (CS), with rates increasing worldwide. In 2022, China experienced a cesarean section rate of 45% [ 6 ]. A history of previous cesarean section is an important cause contributing to the risk of uterine rupture [ 1 , 22 , and 23 ]. A cesarean section leaves behind a surgical scar on the uterus. The healing process can result in the formation of fibrous scar tissue, which is less elastic and more prone to rupture compared to healthy uterine tissue. The rate of uterine rupture is approximately 1% for women with one previous cesarean delivery versus 3.9% for those with greater than one previous cesarean delivery [ 24 ]. In our study, 95 had a history of prior cesarean section, accounting for 73.64% of the cases, of which 38 had a history of two or more CS. Current research [ 25 ] shows that intervals shorter than 12 to 18 months are a high-risk factor for uterine rupture, while the optimal window for healing of a cesarean section scar is between 2 and 3 years post-surgery [ 26 ]. After a period exceeding five years, the degree of muscularization in the uterine scar will gradually deteriorate and it will lose elasticity, increasing the risk of uterine rupture during subsequent pregnancies [ 27 ]. In this study, the median interval from last CS was 5 years, ranging from 1 to 14 years. The incidence of uterine rupture in our study was 0.12% in those with a history of cesarean section. Our study showed that the surgical operation of D&C is also a main risk factor of uterine rupture. Previous study [ 28 ] has reported that D&C can lead to damage of the endometrium, the uterine muscular wall or even result in uterine perforation, which can contribute to weakening the uterine wall. Then fragile tissue can lead to rupture at the weak points of the uterus due to excessive distension during late pregnancy or overly strong contractions during childbirth. The rupture of the uterus at earlier gestational weeks may be related to greater local tension on the uterine floor and body scars during pregnancy [ 29 ]. Abortion-induced partial damage to the endometrium, pathological changes in the uterine muscle fibers, thinning of the muscular wall, Of the 129 cases, 77 (59.7%) had a history of dilation and curettage (D&C), with 15 who had severe postpartum hemorrhage and three who underwent hysterectomies. The high rate of abortion curettage also highlights the need for enhanced sex education in our country. There is insufficient awareness about proper contraception, and artificial abortions, including repeated ones, increase the risk of uterine damage and scarred uterus. The risk of uterine rupture due to placental accreta is 20.82 times higher compared to non-placental accreta [ 30 ]. When the uterus has inflammation or scars, the placenta is more likely to attach. Due to changes in the endometrial thickness and the elasticity of the muscular tissue after placental accreta, uterine rupture is more likely to occur and its symptoms are less obvious. In this study, 11 patients had placenta accreta, with seven who had severe postpartum hemorrhage and two who underwent hysterectomies.Exposure to oxytocin. It is known that prolonged uterine exposure to oxytocin and other uterotonic medications increases uterine wall stress and may lead to rupture [ 31 – 32 ]. Women who experience a uterine rupture are more likely to have received oxytocin for induction compared to women without a rupture [ 33 ]. In this review, 15 patients underwent labor induction with oxytocin, including seven cases where ethacridine was utilized. The use of pharmacological induction in women with a history of cesarean delivery is associated with an extremely high incidence of uterine rupture [ 34 ]. Six patients had a previous CS. None of the nine cases had a history of cesarean section, but seven of them had a history of D&C. This result also suggests that the combined use of oxytocin in patients with a history of D&C is risky. Therefore, when pregnant women with scarred uterus have to undergo labor induction during the middle and late stages of pregnancy, it is essential to closely monitor the condition of abdominal pain, especially if there is a sudden relief after severe abdominal pain, as this may indicate the occurrence of uterine rupture. Our study showed that the most common clinical symptom was abdominal pain (41%), followed by vaginal bleeding (14%) [ 35 – 36 ], and 45% of patients with uterine rupture did not experience these symptoms [ 36 ]. In this review, it was found that the group exhibiting clinical symptoms such as abdominal pain or vaginal bleeding demonstrated a notably higher preoperative diagnosis rate, an increased frequency of neonatal ICU admissions, and reduced birth weights. It is suggested that abdominal pain and vaginal bleeding are very common in pregnant women with uterine rupture, which are easy to attract the attention of healthcare workers, so the preoperative diagnosis rate is relatively high. These symptoms often indicate a more advanced stage of rupture, which may tend to have poor fetal outcomes. In some cases, the symptoms may be subtle or absent, especially if the rupture is small or contained. In a stable patient with a possible minor rupture, an ultrasound can be helpful to diagnose [ 23 ]. The following abdominal ultrasound findings support the diagnosis of uterine rupture: abnormal uterine wall, a hematoma adjacent to a hysterectomy scar, free fluid in the peritoneum, anhydramnios, or fetal parts outside the uterus [ 37 – 38 ]. For the radiographic identification of uterine rupture, emphasis should be placed on monitoring the continuity of the lower segment myometrium [ 39 ]. Kok et al. [ 40 ] reported that in late pregnancy ultrasound examinations, when B-ultrasound indicates a lower uterine segment scar thickness less than 2.3–2.5 mm, the risk of uterine rupture increases. Recognized as the preferred imaging method for evaluating acute abdominal conditions in pregnant women, the detection rate for signs of uterine rupture ranges from 36 to 77% [ 41 ].In this study, the proportion of uterine rupture cases with abdominal pain symptoms detected by ultrasound was 26.4%, primarily manifested as peritoneal fluid, discontinuity in the myometrium and signs of placental abruption on sonography. This is lower than the proportion reported in the literature, which may be because some cases in this study were treated with direct operation without ultrasonic examination because of their typical clinical manifestations and critical condition. Furthermore, the detection rate of ultrasound is influenced by the precision of the ultrasound equipment, the technical expertise of the sonographer, and the bladder filling status during the examination. Although prenatal ultrasound examination has its limitations, is still an effective means to assist in the early identification of uterine rupture. The major finding of the current study was that patients with uterine rupture during mid-trimester were more likely to receive a blood transfusion (41.67%) and exhibited higher rates of bladder injury (33.33%). We highly suspect that this adverse pregnancy outcome is the result of a combination of factors, including a higher rate of uterine surgery history (100%), placental implantation (25%), and increased use of oxytocin (33.33%) and TOLAC rates (50%) in patients with mid-trimester uterine rupture. Among the 12 pregnant women who experienced uterine rupture in the second trimester, eight had a history of cesarean section, seven had a history of dilation and curettage(six had a history of both CS and D&C), two had a history of ectopic pregnancy tubal surgery, and one had a history of high-intensity focused ultrasound ablation for adenomyosis. The thermal ablation procedure for adenomyosis can cause degeneration and necrosis of uterine myometrial cells, leading to structural changes in the uterine muscular layer and damage to the endometrium [ 21 ]. Uterine surgery causes structural changes in the uterine muscular layer, leading to reduced elasticity and functional abnormalities of the uterine muscle layer. This makes it more likely for conditions such as placental accreta to develop; thereby increasing the risk of uterine rupture during pregnancy [ 42 ].Three patients had placenta accrta. A meta-analysis showed that TOLAC results in a 0.27% higher risk of uterine rupture [ 43 ]. Four patients attempted a TOLAC in the second-trimester uterine rupture, and all four received oxytocin. TOLAC requires comprehensive management and assessment of the entire labor process and high-risk factors for pregnant women. A uterine rupture should be considered in all women undergoing a TOLAC if any of the following occurs: hypotension, a sudden change in contraction pattern, fetal bradycardia, sudden abdominal pain, hematuria, loss of fetal station, or vaginal bleeding [ 23 ]. The expert consensus in our country [ 44 ] lists a history of two or more uterine surgeries as a contraindication for TOLAC.Because pregnant women in mid-pregnancy have an early gestation age and only 6/12 of them exhibit clinical symptoms, it is less likely to suspect uterine rupture. Since the clinical symptoms of uterine rupture were atypical and might easily be misdiagnosed as preterm delivery [ 28 ].Two patients were sent to hospital by their family members 6 h after abdominal pain, they both experienced postpartum hemorrhage, and one underwent hysterectomy. This also indicates that the two pregnant women and their families lack sufficient understanding of uterine rupture. A risk-graded early warning system for pregnant women in the second trimester with a history of uterine surgery should be attempted to establish. The possibility of uterine rupture should be highly suspected for pregnant women in the second trimester with persistent abdominal pain, abdominal effusion, and fetal distress. When an induction of labor is unavoidable in the middle and late stages of pregnancy for women with scarred uterus, it is necessary to closely monitor the situation of abdominal pain; and one should be vigilant about the possibility of uterine rupture. At the same time, physical examination and monitoring of vital signs are also very important. If a pregnant woman in the second trimester with scarred uterus who choose TOLAC should fully understand the pros and cons of VBAC (vaginal birth after cesarean section), and have close monitoring and management in the entire labor process, with timely assessment.