Obstetrics & Gynecology:
The Role of Uterine Closure in the Risk of Uterine Rupture
Bujold, Emmanuel MD, MSc, FRCSC; Goyet, Martine MD, FRCSC; Marcoux, Sylvie MD, PhD; Brassard, Normand MD, MBA, FRCSC; Cormier, Béatrice MD; Hamilton, Emily MD, FRCSC; Abdous, Belkacem PhD; Sidi, Elhadji A. Laouan MSc; Kinch, Robert MD, FRCSC; Miner, Louise MD, FRCSC; Masse, André MD, FRCSC; Fortin, Claude MD, FRCSC; Gagné, Guy-Paul MD, FRCSC; Fortier, André MD, FRCSC; Bastien, Gilles MD, PhD, CCFP; Sabbah, Robert MD, FRCSC; Guimond, Pierre MD, FRCSC; Roberge, Stéphanie MSc; Gauthier, Robert J. MD, FRCSC
From the Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre Hospitalier Universitaire de Québec, Université Laval, Québec, Canada, the Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, Canada, and the Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpital Sainte-Justine, Université de Montréal, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpital Sainte-Justine, Université de Montréal, Montréal, Quebec Canada, and the Department of Obstetrics & Gynaecology, Hôpital Lasalle, Lasalle, Quebec, Canada; the Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre Hospitalier Universitaire de Québec, Université Laval, Québec, Canada, and the Department of Obstetrics & Gynaecology, Faculty of Medicine, St Mary's Hospital, McGill University, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Royal Victoria Hospital, McGill University, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Royal Victoria Hospital, McGill University, Montréal, Quebec, Canada; Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, Canada; Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Royal Victoria Hospital, McGill University, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Jewish General Hospital, McGill University, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre Hospitalier de l'Université de Montréal (CHUM), Université de Montréal, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Hôpital Lasalle, Lasalle, Quebec, Canada; the Department of Obstetrics & Gynaecology, Hôpital Lasalle, Lasalle, Quebec, Canada; the Department of Obstetrics & Gynaecology, Hôpital Pierre-Boucher, Longueuil, Quebec, Canada; the Department of Obstetrics & Gynaecology, Centre Hospitalier Cité de la Santé, Laval, Quebec, Canada; Department of Obstetrics & Gynaecology, Hôpital Sacré-Coeur, Université de Montréal, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, Quebec, Canada; the Department of Obstetrics & Gynaecology, Faculty of Medicine, Centre Hospitalier Universitaire de Québec, Université Laval, Québec, Canada, and the Department of Social and Preventive Medicine, Faculty of Medicine, Université Laval, Québec, Quebec, Canada; and the Department of Obstetrics & Gynaecology, Faculty of Medicine, Hôpital Sainte-Justine, Université de Montréal, Montréal, Quebec, Canada.
Dr Emmanuel Bujold holds a Clinician Scientist Award from the Canadian Institutes of Health Research and the Jeanne and Jean-Louis Lévesque Perinatal Research Chair at Université Laval. This study was funded by the Canadian Foundation for Women's Health and the Jeanne and Jean-Louis Lévesque Perinatal Research Chair at Université Laval and by the Fonds de Recherche des Gynécologues-Obstétriciens de l'Hôpital Sainte-Justine (FOREGO).
Ovid DaSilva provided English editing assistance.
Corresponding author: Emmanuel Bujold, MD, MSc, FRCSC, Associate Professor, Department of Obstetrics and Gynaecology, Faculty of Medicine, Université Laval, 2705, boulevard Laurier, Québec, QC, Canada G1V 4G2; e-mail: firstname.lastname@example.org.
Financial Disclosure The authors did not report any potential conflicts of interest.
OBJECTIVE: To evaluate the effects of prior single-layer compared with double-layer closure on the risk of uterine rupture.
METHODS: A multicenter, case–control study was performed on women with a single, prior, low-transverse cesarean who experienced complete uterine rupture during a trial of labor. For each case, three women who underwent a trial of labor without uterine rupture after a prior low-transverse cesarean delivery were selected as control participants. Risk factors such as prior uterine closure, suture material, diabetes, prior vaginal delivery, labor induction, cervical ripening, birth weight, prostaglandin use, maternal age, gestational age, and interdelivery interval were compared between groups. Conditional logistic regression analyses were conducted.
RESULTS: Ninety-six cases of uterine rupture, including 28 with adverse neonatal outcome, and 288 control participants were assessed. The rate of single-layer closure was 36% (35 of 96) in the case group and 20% (58 of 288) in the control group (P<.01). In multivariable analysis, single-layer closure (odds ratio [OR] 2.69; 95% confidence interval [CI] 1.37–5.28) and birth weight greater than 3,500 g (OR 2.03; 95% CI 1.21–3.38) were linked with increased rates of uterine rupture, whereas prior vaginal birth was a protective factor (OR 0.47; 95% CI 0.24–0.93). Single-layer closure was also related to uterine rupture associated with adverse neonatal outcome (OR 2.89; 95% CI 1.01–8.27).
CONCLUSION: Prior single-layer closure carries more than twice the risk of uterine rupture compared with double-layer closure. Single-layer closure should be avoided in women who could contemplate future vaginal birth after cesarean delivery.
LEVEL OF EVIDENCE: II
Although rare, the catastrophic complications of uterine rupture make it one of the worst obstetric emergencies. Moreover, its rapid evolution can hamper the best rescue efforts.1–3 Obstetricians are well acquainted with unforeseeable labor complications that require rapid intervention to avoid injury such as cord prolapse or amniotic fluid embolism. Uterine rupture is different because the decision to undergo a trial of labor, and hence accepting exposure to this known risk, usually results from a deliberate process involving both the obstetrician and mother. It follows that good estimates are required of the independent effects of various risk factors. Some risk factors are not modifiable, but some are potentially changeable such as medical interventions related to the management of labor and delivery.
The current study aims to examine the independent contribution of several risk factors of uterine rupture to help clinicians more accurately assess and communicate the risks to mothers and they can make informed clinical choices about risk factors. One of the key potential risk factors we examine that is modifiable is the technique of uterine closure in prior cesarean delivery.4
More than one million cesarean deliveries are performed every year in North America.5 Although the technique of low-transverse cesarean delivery is by far the most commonly performed, some technical aspects of the procedure remain controversial. Closure of the uterus is one step in the operative procedure for which there is no consensus.6 Although two-layer closure was almost exclusively common practice two decades ago, single-layer closure, associated with shorter operative time and fewer hemostatic sutures, gained popularity in the 1990s and is in common use today.7,8 However, in 2002, a retrospective study showed a fourfold increase in the risk of uterine rupture with prior single-layer closure compared with double-layer closure in women undergoing a trial of labor after prior cesarean delivery.4,9 With more than 500,000 women with previous cesarean delivery in North America and more than a million around the world deciding about possibly undergoing a trial of labor every year, it is imperative to confirm whether a simple change in the cesarean surgical technique, such as the number of layers for uterus closure, could affect the incidence of uterine rupture.5 Therefore, we have evaluated the independent contributions of several risk factors for uterine rupture, including the method of uterine closure (single layer compared with double layer) at previous cesarean delivery.
We performed a multicenter, case–control study comparing women who experienced complete uterine rupture during a trial of labor after prior, single, low-transverse cesarean delivery with a group of control participants who underwent a trial of labor after a prior, single, low-transverse cesarean delivery without uterine rupture of any degree. Patients for the case and control groups were selected from deliveries at 10 centers in the Montreal metropolitan area between 1992 and 2002. This period was predetermined to avoid potential obstetric practice changes in regard to type of uterine closure that could have occurred after the publication of studies by Bujold et al.4,9 All women with a documented low-transverse cesarean delivery who underwent a trial of labor after 24 weeks of gestation were eligible irrespective of the final mode of delivery. Exclusion criteria included all the standard contraindications to attempting a vaginal birth after cesarean (prior classical or J-shaped uterine scar, previous extension above the low transverse incision, prior transmural myomectomy, placenta praevia) as well as the presence of more than one prior cesarean delivery or birth weight under 500 g. Uterine rupture was defined as complete opening of the uterus, including the visceral serosa or vesical wall, confirmed at the time of cesarean delivery or during immediate postpartum laparotomy.10 Women with incomplete uterine rupture or “uterine dehiscence,” defined as an opening of the uterus with intact visceral serosa, were excluded and were not eligible to be control participants. Patients for the case group were identified by International Classification of Diseases, 9th Revision code (665.0, 665.1, 674.1) in the medical records combined with local perinatal databases when available. All charts were reviewed by a physician (M.G. or B.C.) for eligibility and data collection. In case of uncertainty regarding eligibility, the charts were reviewed independently by two other physicians (E.B., R.J.G.) who were blinded to the prior type of closure to reach a consensus. Control participants were selected from the list of patients with prior cesarean delivery (International Classification of Diseases, 9th Revision, Clinical Modification code 654.2) who delivered before the case of uterine rupture in the same center. Medical charts were reviewed in reverse chronological sequence starting from each case of uterine rupture to find the first three control participants that met the eligibility criteria. Control participants were selected from among patients treated before each index case to avoid bias from a potential obstetric practice change that might occur in the days or weeks after a case of uterine rupture. Therefore, patients in the case and control groups were matched by time period and hospital. After the case and control groups had been established for each center, all charts were reviewed to record maternal age and maternal weight at the time of delivery, gravidity, parity, gestational or pregestational diabetes, indication and date of the prior cesarean delivery, birth weight of the neonate from prior cesarean delivery, date of the current delivery, induction of labor, cervical maturation (use of prostaglandins or intracervical Foley catheter), oxytocin use, birth weight, Apgar score, umbilical cord pH, intrapartum or neonatal death, and maternal morbidity, including blood transfusion and peripartum hysterectomy. When the prior operative report was available in the maternal chart, we noted the method of uterine closure and type of suture material. The interdelivery interval was calculated in months from the prior cesarean delivery to the current delivery.
Univariable and multivariable conditional regression analyses were performed for predetermined potential risk factors of uterine rupture. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated. Proportions were compared using chi square and Fisher's exact tests when appropriate. All statistical tests were two-sided; P<.05 was considered significant. The primary independent variable was type of closure (single layer, double layer, unknown). Multivariable conditional logistic regression analysis was conducted to calculate the adjusted OR for adjusting for the effect of each variable associated with uterine rupture with a P<.10 in univariable analysis as well as the birth center (that was used for matching). The following variables were considered: maternal age, maternal weight at delivery (or the closest available weight if taken after 28 weeks of gestation), prior vaginal delivery, prior vaginal birth after cesarean delivery, gestational or pregestational diabetes, indication for the previous cesarean delivery (arrest disorder or not), induction of labor, with favorable or unfavorable cervix (defined as Bishop's score less than 7 or cervical dilatation less than 2 cm if Bishop's score was not available), cervical maturation (use of prostaglandins or intracervical Foley catheter), oxytocin use, birth weight, birth weight at the previous cesarean delivery, method of uterine closure at the previous cesarean delivery, and type of suture material.
A secondary analysis was performed, excluding those patients from Sainte-Justine Hospital who were included in the prior publication of Bujold et al.4 Finally, we conducted a third analysis among women who experienced uterine rupture associated with adverse neonatal outcome and their respective control participants to determine whether any of the risk factors independently increased the likelihood of adverse neonatal outcome because this event was of great concern for the majority of women contemplating vaginal birth after cesarean. For this analysis, adverse neonatal outcome was defined as arterial cord blood pH less than 7.0 or 5-minute Apgar score less than 4 or intrapartum fetal death. The stepwise logistic regression analysis included all significant variables.
Sample size calculation during the planning phase was based on our prior experience. We estimated that approximately 25% of those in the control group would have had single-layer closure, as would at least 50% of the those in the case group. To obtain a significant difference, with an α error of .05 and a β error of .10, with three control participants for each case of uterine rupture and an OR of 2 or more, a minimum of 55 cases of uterine rupture and 165 control participants would be necessary. We estimated that 3–5% of deliveries during the study period would have been patients undergoing a trial of labor after a single prior cesarean delivery. Assuming a rate of uterine rupture of 0.8%, we estimated that we would need a cohort of at least 137,500 deliveries and possibly up to 230,000 deliveries to find sufficient patients for the case and control groups. Study participation was, therefore, proposed to all departments of obstetrics and gynecology of Montreal hospitals that counted more than 2,000 deliveries per year. The research protocol was approved by the department head and the Ethics Review Board of each center.
Altogether, approximately 288,000 deliveries were recorded in the 10 participating centers between 1992 and 2002. One center did not have a single case of complete uterine rupture during the study period. Ninety-six cases of uterine rupture and 288 control participants were identified in the other nine centers.
Among the 96 cases, rupture was diagnosed intrapartum in 89 (93%) and postpartum by laparotomy in seven (7%). Of these seven, three occurred in women with a previous single-layer closure and four in women with a double-layer closure. Six (6%) of the cases were accompanied by intrapartum fetal death, 29 (30%) had neonates with 5-minute Apgar scores less than 7, and 16 (17%) had neonates with 5-minute Apgar scores less than 4. In the 76 with arterial blood gas measurements, 24 (32%) had pH less than 7.0. Twenty-eight (29%) neonates had 5-minute Apgar scores less than 4, arterial umbilical cord pH less than 7.0, or intrapartum fetal death. Thirteen (14%) mothers received blood transfusions. There were no intrapartum or postpartum maternal deaths before discharge. Among the 288 control participants, 210 (73%) succeeded in achieving a vaginal delivery.
Maternal and obstetric characteristics for patients in the case and control groups are reported in Table 1. Among the 13 risk factors, univariable analysis identified seven with a statistically significant association with uterine rupture. Uterine rupture was linked to single-layer closure of the uterus with an OR of 2.51 (95% CI 1.45–4.36). Other factors related to uterine rupture included birth weight less than 3,500 g, interdelivery interval less than 24 months, labor induction with an unfavorable cervix, oxytocin use for labor induction or augmentation, and gestational age at delivery 41 weeks of gestation or greater. In keeping with numerous other studies, we found that prior vaginal birth was associated with diminished risk of uterine rupture.11,12 The suture material used for uterine closure was comparable for those in the case and control groups.
Mutivariate conditional regression analysis was performed according to the seven factors identified through univariable analysis as well as the birth center (Table 1). After adjustment, single-layer closure and birth weight greater than 3,500 g remained associated with uterine rupture, whereas prior vaginal birth stayed as a protective factor. Multivariable regression analysis was repeated after exclusion of the 23 cases of uterine rupture reported previously from Sainte-Justine Hospital and their 69 appropriate control participants.4 In that secondary analysis, single-layer closure of the uterus remained associated with uterine rupture (OR 2.36; 95% CI 1.10–5.07) (data not shown). We evaluated the effect of center type according to the presence or the absence of an obstetrics–gynecology residency program. We found that surgeons from centers with obstetrics–gynecology residency program were more likely to use single-layer closure (30% [48 of 159] of the control participants) and the association between single-layer closure and uterine rupture was very significant (OR 3.59; 95% CI 1.62–7.99). On the other hand, centers without a obstetrics–gynecology residency program were less likely to use single-layer closure (8% [10 of 129] of the control participants) and the association was not significant (OR 0.77; 95% CI 0.17–3.57).
Finally, the analysis was repeated in only the 28 cases associated with adverse neonatal outcomes (pH less than 7.0, 5-minute Apgar scores less than 4, intrapartum fetal death) and their respective control participants (Table 2). With stepwise logistic regression analysis, we observed that single-layer closure remained the only significant factor related to uterine rupture with adverse neonatal outcome.
The study has demonstrated that among a number of purported risk factors for uterine rupture, only three were independently associated and just one was potentially modifiable. A single-layer closure in the previous cesarean delivery carried over a twofold increase in risk followed closely by a birth weight in the current pregnancy greater than 3,500 g, whereas a prior vaginal delivery decreased the risk by nearly half. Of these three factors, only a prior single-layer closure affected the risk of uterine rupture associated with an adverse neonatal outcome. We further established that it was presence of the single-layer closure itself, not the suture material, that was associated with the rupture.
Our study has some limitations. We could not examine every possible variable such as clinical complications or level of the surgeon's expertise at the time of the first cesarean delivery or aspects of management during the labor complicated by uterine rupture such as the amount and duration of oxytocin use. Nevertheless, among the factors examined, three stood apart from all the others. On the other hand, the strengths of our study are numerous and include its multicenter design, the large number of cases, an unequivocal definition of uterine rupture, and thorough review of the actual charts resulting in high levels of data accuracy. Control participants were selected to account for local practice patterns and changes over the years. The study was performed in a period when the method of previous uterine closure was not believed to be related to uterine rupture and thus did not affect decisions about a trial of labor.
The literature provides inconsistent conclusions regarding the role of the uterine closure technique and subsequent uterine rupture. Most studies have compared rates of uterine rupture in two groups defined by previous closure technique. The sample size necessary to study a relatively rare complication such as uterine rupture with an expected incidence of approximately 1% and anticipating a difference between groups as large as 50% would be approximately 10,000 women undergoing a trial of labor. To date, most cohort studies examining the role of single- compared with double-layer closure involved fewer than 1,000 patients. Guise et al recently reviewed the literature regarding closure type and uterine rupture risk and concluded that there were serious methodological deficiencies precluding a clear answer on the role of uterine closure.4,13–17 The only randomized trial reported by Chapman et al involved 906 women who were randomized to single- compared with double-layer uterus closure. Only 164 of them had subsequent pregnancies and no uterine rupture was reported. In short, these previous studies were greatly underpowered to examine rates of uterine rupture according to uterine closure technique. The current study applies a different technique, namely conditional multiple regression, applied to a large retrospective sample of women with uterine rupture and matched control participants to measure the independent effect of interrelated risk factors. This study examined 96 uterine ruptures, which is more than the 62 cases in all the other studies combined.14–18
We do not have a precise understanding of the pathophysiology involved in the association of the single-layer closure technique and subsequent uterine rupture; however, some observations and speculations support our findings. It is possible that a single, continuous suture technique does not approximate the tissues precisely together because decidua can be included in the scar. Poidevin19 demonstrated, in several animal models, that decidua inclusion in the scar or eversion or both of the hysterotomy edge are important factors related to subsequent uterine scar defect. Scar thickness measurements, which were not available to us, would have been an interesting way of further examining this mechanism.20–22 Uterine rupture is thought to result from a biomechanical process, in which there is an imbalance between the tensile strength of the scar that maintains its integrity and the forces causing disruption.23 None of these forces is directly measurable today. However, it is plausible that a thinner or weaker scar would be more prone to rupture. Further studies are definitely required to explain the association between single-layer closure and uterine rupture.
The magnitude of the association we observed between single-layer closure and uterine rupture makes this information crucial to all women and healthcare providers who are making choices about the mode of delivery and all surgeons performing cesarean deliveries. Moreover, it has been shown that the double-layer technique is as easy to perform as the single-layer technique in most cases.7 Given the information available today, we agree with Jelsema et al24 that single-layer closure be reserved for women undergoing tubal ligation or those who require very expedient closure of the uterus.
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This article has been cited 3 time(s).
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International Journal of Obstetric AnesthesiaChronic pain after childbirthInternational Journal of Obstetric Anesthesia
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