Lower uterine segment thickness to prevent uterine rupture and adverse perinatal outcomes: a multicenter prospective study.

BACKGROUND: Choice of delivery route after previous cesarean delivery can be difficult because both trial of labor after cesarean delivery and elective repeat cesarean delivery are associated with risks. The major risk that is associated with trial of labor after cesarean delivery is uterine rupture that requires emergency laparotomy. OBJECTIVE: This study aimed to estimate the occurrence of uterine rupture during trial of labor after cesarean delivery when lower uterine segment thickness measurement is included in the decision-making process about the route of delivery. STUDY DESIGN: In 4 tertiary-care centers, we prospectively recruited women between 34 and 38 weeks of gestation who were contemplating a vaginal birth after a previous single low-transverse cesarean delivery. Lower uterine segment thickness was measured by ultrasound imaging and integrated in the decision of delivery route. According to lower uterine segment thickness, women were classified in 3 risk categories for uterine rupture: high risk (<2.0 mm), intermediate risk (2.0-2.4 mm), and low risk (≥2.5 mm). Our primary outcome was symptomatic uterine rupture, which was defined as requiring urgent laparotomy. We calculated that 942 women who were undergoing a trial of labor after cesarean delivery should be included to be able to show a risk of uterine rupture <0.8%. RESULTS: We recruited 1856 women, of whom 1849 (99%) had a complete follow-up data. Lower uterine segment thickness was <2.0 mm in 194 women (11%), 2.0-2.4 mm in 217 women (12%), and ≥2.5 mm in 1438 women (78%). Rate of trial of labor was 9%, 42%, and 61% in the 3 categories, respectively (P<.0001). Of 984 trials of labor, there were no symptomatic uterine ruptures, which is a rate that was lower than the 0.8% expected rate (P=.0001). CONCLUSION: The inclusion of lower uterine segment thickness measurement in the decision of the route of delivery allows a low risk of uterine rupture during trial of labor after cesarean delivery.

Adverse obstetric outcomes in women with previous cesarean for dystocia in second stage of labor.

OBJECTIVE: To evaluate obstetric outcomes in women undergoing a trial of labor (TOL) after a previous cesarean for dystocia in second stage of labor. METHODS: A retrospective cohort study of women with one previous low transverse cesarean undergoing a first TOL was performed. Women with previous cesarean for dystocia in first stage and those with previous dystocia in second stage were compared with those with previous cesarean for nonrecurrent reasons (controls). Multivariable regressions analyses were performed. RESULTS: Of 1655 women, those with previous dystocia in second stage of labor (n = 204) had greater risks than controls (n = 880) to have an operative delivery [odds ratio (OR): 1.5; 95% confidence intervals (CI) 1.1 to 2.2], shoulder dystocia (OR: 2.9; 95% CI 1.1 to 8.0), and uterine rupture in the second stage of labor (OR: 4.9; 95% CI 1.1 to 23), and especially in case of fetal macrosomia (OR: 29.6; 95% CI 4.4 to 202). The median second stage of labor duration before uterine rupture was 2.5 hours (interquartile range: 1.5 to 3.2 hours) in these women. CONCLUSION: Previous cesarean for dystocia in the second stage of labor is associated with second-stage uterine rupture at next delivery, especially in cases of suspected fetal macrosomia and prolonged second stage of labor.

Reliability of 3-dimensional transvaginal sonographic measurement of lower uterine segment thickness.

OBJECTIVES: The purpose of this study was to report the intraobserver and interobserver reliability of transvaginal 3-dimensional (3D) sonographic measurement of lower uterine segment thickness. METHODS: A prospective study of 60 pregnant women with previous low transverse cesarean deliveries was performed between 35 and 39 weeks' gestation. Two observers, blinded to the clinical data, independently measured the full lower uterine segment thickness by 2-dimensional (2D) transvaginal sonography. Three-dimensional volume data sets of the lower uterine segment were captured and analyzed more than 2 months later by both observers independently. Intraobserver, interobserver, and intermethod reliability was evaluated by median absolute differences, nonparametric limits of agreement, intraclass correlation coefficients (ICCs), and κ coefficients. RESULTS: The median full lower uterine segment thickness was 3.6 mm (range, 0.9-8.0 mm). Intraobserver reliability (median difference, 0.3 mm [interquartile range (IQR), 0.1-0.6 mm]; ICC, 0.88 [95% confidence interval (CI), 0.81-0.93]; κ, 0.87 [95% CI, 0.69-1.00]) and interobserver reliability (median difference, 0.3 mm [IQR, 0.1-0.5 mm]; ICC, 0.88 [95% CI, 0.81-0.93]; κ, 0.86 [95% CI, 0.66-1.00]) were excellent. Reliability between 3D and 2D sonography was moderate (median difference, 0.6 mm [IQR, 0.2-0.9 mm]; ICC, 0.78 [95% CI, 0.66-0.86]; κ, 0.56 [95% CI, 0.28-0.85]). However, intermethod reproducibility was improved when the full lower uterine segment thickness was less than 3.0 mm (median difference, 0.4 mm [IQR, 0.2-0.9 mm]). CONCLUSIONS: Full lower uterine segment thickness measured with 3D transvaginal sonographic data sets has excellent intraobserver and interobserver reliability. It also has good reproducibility with 2D sonography when the full lower uterine segment thickness is less than 3.0 mm.

Reliability of two-dimensional transvaginal sonographic measurement of lower uterine segment thickness using video sequences.

OBJECTIVES: To report the intra- and interobserver reliability of measurement of the lower uterine segment (LUS) thickness using transvaginal sonographic videos. METHODS: A prospective study of 60 women with previous, low-transverse cesarean undergoing LUS examination (36 to 39 weeks) was performed. Two observers independently measured full LUS thickness using transvaginal sonography. A video of the LUS was recorded and analyzed more than 2 months later by both observers. Intra- and interobserver reliability was assessed with median absolute differences and interquartile range (IQR), nonparametric limits of agreement, intraclass correlation coefficients (ICC) with 95% confidence interval (95% CI), and kappa coefficients. RESULTS: Median full LUS thickness was 3.6 mm (range: 0.9 to 8.0 mm). Intraobserver repeatability was excellent (median difference: 0.2 mm, IQR: 0.1 to 0.4; ICC: 0.94, 95% CI: 0.90 to 0.96; kappa: 1.00). Interobserver (median difference: 0.3 mm, IQR: 0.2 to 1.3; ICC: 0.91, 95% CI: 0.86 to 0.95; kappa: 0.76, 95% CI: 0.54 to 0.98) and intermethod reproducibility (median difference: 0.4 mm, IQR: 0.2 to 0.8; ICC: 0.82, 95% CI: 0.72 to 0.89; kappa: 0.69, 95% CI: 0.43 to 0.94) were good. However, both interobserver and intermethod reproducibility were improved when LUS thickness was below 3 mm. CONCLUSION: Full LUS thickness measured from transvaginal sonographic videos has excellent intra- and interobserver reproducibility and good reproducibility with live transvaginal ultrasound.

Factors associated with lower uterine segment thickness near term in women with previous caesarean section.

OBJECTIVE: To estimate the association between potential influencing factors and lower uterine segment (LUS) thickness at term in women with previous Caesarean section. METHODS: We conducted a cohort study of women with previous low-transverse Caesarean section undergoing ultrasonographic measurement of LUS thickness between 35 and 38 weeks' gestation in a tertiary care centre between 2006 and 2009. Measurements of the full LUS thickness and the myometrial LUS thickness were performed both transabdominally and transvaginally. The thinnest measurements for both full and myometrial LUS thicknesses were considered dependent variables. Non-parametric analyses, multivariate linear regression analyses, and multivariate regression analyses were used to evaluate the relationships between LUS thickness and the potential influencing factors of maternal age, interdelivery interval, prior vaginal delivery, and several characteristics of the previous Caesarean section. RESULTS: In 377 women who underwent measurement of LUS thickness, labour before previous Caesarean section was the only characteristic associated with a greater full LUS thickness (an additional 0.9 mm; 95% CI 0.5 to 1.2 mm) in multivariate linear regression analysis. Labour before previous Caesarean section (0.5 mm; 95% CI 0.2 to 0.7 mm) and the use of synthetic sutures (as opposed to catgut sutures) for the closure of the previous hysterotomy incision (0.3 mm; 95% CI 0.02 to 0.5 mm) were the only two variables significantly associated with a thicker myometrial LUS. In multivariate regression analysis, three factors were predictive of a full LUS thickness of > 2.3 mm: the presence of labour, a recurrent indication for Caesarean section, and the use of synthetic sutures for hysterotomy closure at previous Caesarean section (P < 0.05). CONCLUSION: Labour at the time of previous Caesarean section is associated with a thicker LUS near term in the subsequent pregnancy. The use of synthetic sutures for hysterotomy closure is another factor potentially associated with a thicker LUS.

Single- versus double-layer closure of the hysterotomy incision during cesarean delivery and risk of uterine rupture.

OBJECTIVE: To evaluate the best available evidence regarding the association between single-layer closure and uterine rupture. METHODS: The PubMed, Embase, and Cochrane Central Register of Controlled Trials databases were searched for relevant observational and experimental studies that included women with a previous single, low, transverse cesarean delivery who had attempted a trial of labor (TOL). The risks of uterine rupture and uterine dehiscence were assessed by pooled odds ratios (OR) calculated with a random effects model. RESULTS: Nine studies including 5810 women were reviewed. Overall, the risk of uterine rupture during TOL after a single-layer closure was not significantly different from that after a double-layer closure (OR 1.71; 95% confidence interval [CI] 0.66-4.44). However, a sensitivity analysis indicated that the risk of uterine rupture was increased after a locked single-layer closure (OR 4.96; 95% CI 2.58-9.52, P<0.001) but not after an unlocked single-layer closure (OR 0.49; 95% CI 0.21-1.16), compared with a double-layer closure. CONCLUSION: Locked but not unlocked single-layer closures were associated with a higher uterine rupture risk than double-layer closure in women attempting a TOL.

The role of uterine closure in the risk of uterine rupture.

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.

[Measurement of the lower uterine segment: are we ready for a clinical application?]. / Mesure du segment inférieur utérin : sommes-nous prêts pour une application clinique ?

The measurement of the lower uterine segment (LUS) seems to be the best technique available to estimate the risk of uterine rupture, but there is a great heterogeneity in the techniques used. It appears necessary to standardize the interventions and their teaching prior to extending the use of the LUS measurement to clinical settings beyond well-defined research purposes.

Effect of birth weight on adverse obstetric outcomes in vaginal birth after cesarean delivery.

OBJECTIVE: To estimate the association between neonatal birth weight and adverse obstetric outcomes in women attempting vaginal birth after cesarean. METHODS: We reviewed the medical records of all women undergoing a trial of labor after a prior low transverse cesarean delivery in our institution between 1987 and 2004. Patients were categorized according to birth weight (less than 3,500 g [group 1, reference], 3,500-3,999 g [group 2], and 4,000 g or more [group 3]) and prior vaginal delivery. The rates of failed trial of labor, uterine rupture, shoulder dystocia, and third- and fourth-degree perineal laceration were compared among groups. Multivariable logistic regressions were performed to adjust for potential confounding factors. RESULTS: Of 2,586 women, 1,519 (59%), 798 (31%), and 269 (10%) were included in groups 1, 2, and 3, respectively. Birth weight was directly correlated to the rate of failed trial of labor (19%, 28%, and 38% for groups 1, 2, and 3, respectively; P<.01), uterine rupture (0.9%, 1.8%, and 2.6%; P<.05), shoulder dystocia (0.3%, 1.6%, and 7.8%; P<.01), and third- and fourth-degree perineal laceration (5%, 7%, and 12%; P<.01). After adjustment for confounding variables, birth weight of 4,000 g or more remained associated with uterine rupture (odds ratio [OR] 2.62, 95% confidence interval [CI] 1.001-6.85), failed trial of labor (OR 2.47, 95% CI 1.82-3.34), shoulder dystocia (OR 25.13, 95% CI 9.31-67.86), and third- and fourth-degree perineal laceration (OR 2.64, 95% CI 1.66-4.19). CONCLUSION: Birth weight and specifically macrosomia are linked with failed trial of labor, uterine rupture, shoulder dystocia, and third- and fourth-degree perineal laceration in women who underwent prior cesarean delivery. Estimated fetal weight should be included in the decision-making process for all women contemplating a trial of labor after cesarean delivery. LEVEL OF EVIDENCE: II.

Sonography of lower uterine segment thickness and prediction of uterine rupture.

BACKGROUND: Sonographic evaluation of the lower uterine segment was undertaken to study the degree of thinning and, thus, to predict uterine rupture. However, the best measuring technique and recommended cutoff values remain controversial. CASE: Sonographic evaluation of the lower uterine segment at 36 weeks of gestation in a 31-year-old patient with prior low transverse cesarean delivery revealed a full thickness of 3.6 mm and a myometrial layer of 1.1 mm. Nevertheless, the patient experienced a large uterine rupture during a trial of labor at term. CONCLUSION: In this case, there was a discrepancy between the full thickness and the myometrial layer, which could be representative of the lower uterine segment resistance. Such a case emphasizes the need for a consensus on sonographic measuring techniques for the prediction of uterine rupture.

Comparing rates of trial of labour attempts, VBAC success, and fetal and maternal complications among family physicians and obstetricians.

OBJECTIVES: To determine differences between family physicians and obstetricians in rates of trial of labour (TOL) attempt, vaginal birth after Caesarean section (VBAC) success, and maternal-fetal complications. METHODS: We undertook a database evaluation study in an urban Quebec secondary care hospital centre that serves a multiethnic population. Study subjects were pregnant women with at least one previous Caesarean section (CS), who delivered singletons at St. Mary's Hospital Center between January 1995 and December 2003. Outcomes were rates of TOL attempt, of VBAC success and failure, and of uterine rupture or dehiscence. RESULTS: Of 32 500 singleton deliveries, 3694 (11.4%) women met study criteria. Of these, 3493 (94.6%) were patients of obstetricians, and 201 (5.4%) were patients of family physicians. The TOL attempt rate was 50.6% (1768) and 81.1% (163) for obstetricians and family physicians, respectively (P 0.001). For women having TOL, the VBAC success rate was 64.3% for obstetricians and 76.1% for family physicians (P = 0.002). Rates of uterine rupture or dehiscence in the combined failed and successful VBAC groups were 2.9% for obstetricians and 4.3% for family physicians (P = 0.33) whereas in the failed VBAC group the rates were 7.9% versus 17.9% for the family physicians (P = 0.04). Within delivery outcomes for successful and failed VBAC there were no differences in maternal characteristics and newborn outcomes by physician group. CONCLUSION: More patients of family physicians than of obstetricians attempted TOL and had successful VBAC. Newborn outcomes were similar in the two groups, except that in the failed VBAC group, the family doctors had slightly higher uterine rupture or dehiscence rates; given the low power of this study, further studies are needed to confirm and explain this result. Also, given the similarity in patient profiles, the differences in delivery outcomes may be attributable to differences in physician practice styles.