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ORIGINAL RESEARCH |
From the Departments of Obstetrics and Gynecology at the 1Ohio State University, Columbus, Ohio; 2University of Alabama at Birmingham, Birmingham, Alabama; 3University of Texas Southwestern Medical Center, Dallas, Texas; 4University of Utah, Salt Lake City, Utah; 5University of Chicago, Chicago, Illinois; 6University of Pittsburgh, Pittsburgh, Pennsylvania; 7Wake Forest University, Winston-Salem, North Carolina; 8Thomas Jefferson University, Philadelphia, Pennsylvania; 9Wayne State University, Detroit, Michigan; 10University of Cincinnati, Cincinnati, Ohio, and Columbia University, New York, New York; 11Brown University, Providence, Rhode Island; 12Northwestern University, Chicago, Illinois; 13University of Miami, Miami, Florida; 14University of Tennessee, Memphis, Tennessee; 15University of Texas Health Science Center at San Antonio, San Antonio, Texas; 16University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; 17University of Texas Health Science Center at Houston, Houston, Texas; 18Case Western Reserve University, Cleveland, Ohio; 19Vanderbilt University, Nashville, Tennessee; and 20the National Institute of Child Health and Human Development, Bethesda, Maryland; and 21the George Washington University Biostatistics Center, Washington, DC.
| ABSTRACT |
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METHODS: We conducted a prospective multicenter observational study of women with prior cesarean delivery undergoing trial of labor and elective repeat operation. Maternal and perinatal outcomes were compared among women attempting vaginal birth after multiple cesarean deliveries and those with a single prior cesarean delivery. We also compared outcomes for women with multiple prior cesarean deliveries undergoing trial of labor with those electing repeat cesarean delivery.
RESULTS: Uterine rupture occurred in 9 of 975 (0.9%) women with multiple prior cesarean compared with 115 of 16,915 (0.7%) women with a single prior operation (P = .37). Multivariable analysis confirmed that multiple prior cesarean delivery was not associated with an increased risk for uterine rupture. The rates of hysterectomy (0.6% versus 0.2%, P = .023) and transfusion (3.2% versus 1.6%, P < .001) were increased in women with multiple prior cesarean deliveries compared with women with a single prior cesarean delivery attempting trial of labor. Similarly, a composite of maternal morbidity was increased in women with multiple prior cesarean deliveries undergoing trial of labor compared with those having elective repeat cesarean delivery (odds ratio 1.41, 95% confidence interval 1.021.93).
CONCLUSION: A history of multiple cesarean deliveries is not associated with an increased rate of uterine rupture in women attempting vaginal birth compared with those with a single prior operation. Maternal morbidity is increased with trial of labor after multiple cesarean deliveries, compared with elective repeat cesarean delivery, but the absolute risk for complications is small. Vaginal birth after multiple cesarean deliveries should remain an option for eligible women.
LEVEL OF EVIDENCE: II-2
| PARTICPANTS AND METHODS |
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This analysis represents the primary study hypothesis concerning the cohort of women with a history of cesarean childbirth as part of the MaternalFetal Medicine Units Cesarean Registry.3 Maternal and perinatal outcomes were compared among women with a single prior cesarean delivery and multiple prior cesarean deliveries undergoing trial of labor. We also compared these outcomes among women with multiple prior cesarean deliveries who underwent a trial of labor and those undergoing elective repeat cesarean delivery without labor or other indications for cesarean delivery.
Uterine rupture was defined as a disruption of the uterine muscle and visceral peritoneum or a uterine muscle separation with extension to the bladder or broad ligament found at the time of cesarean delivery or laparotomy following VBAC. Postpartum endometritis was defined as a clinical diagnosis of puerperal uterine infection in the absence of findings suggesting another source.
To estimate sample size for the cesarean registry, we assumed a uterine rupture rate of 0.5% in women with a single prior cesarean delivery and the percentage of those women undergoing trial of labor with multiple prior cesarean deliveries to be 1015%. A sample size of 12,000 women was deemed necessary to detect a relative risk (RR) of 2.53.0 for uterine rupture in women with multiple prior cesarean deliveries with type I error of 5% 2-sided and a power of 80%. The sample size was re-evaluated in 2001 because the rate of multiple prior cesarean deliveries among women undergoing trial of labor was lower than expected (5.4%). We estimated 17,000 trials of labor would be necessary to demonstrate a three-fold increased risk of uterine rupture (given an overall rupture rate of 0.66%). The present study of 17,898 women yields almost 85% power to show a three-fold difference in rupture rate and almost 70% power to detect a RR of 2.5.
To assess further whether multiple prior cesarean delivery was associated with an increased risk for uterine rupture in the trial-of-labor group, three multivariable models were used to control various factors. All three models included oxytocin augmentation, induction, epidural use, and prior vaginal delivery as potential confounders. The years since last cesarean delivery and dilatation at admission were then entered sequentially. Two other multivariable logistic regressions were also used to confirm an increased risk in a maternal composite outcome with multiple prior cesarean deliveries in the trial-of-labor group as well as in women with multiple prior cesarean deliveries undergoing trial of labor compared with elective repeat cesarean delivery. These models controlled for maternal age, race, marital status, tobacco use, insurance status, birth weight, and prior vaginal delivery. Center-to-center variation was assessed but was not found to make a difference in our conclusions. Continuous variables were compared using the Wilcoxon rank-sum test and categorical variables using the
2 or Fisher exact test. Nominal two-sided P values are reported with statistical significance defined as a P < .05. No adjustments were made for multiple comparisons. SAS 8.2 (SAS Institute Inc, Cary, NC) was used for the analyses.
| RESULTS |
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The overall trial-of-labor success rate was 13,138 of 17,890 (73%). Women with a single prior cesarean delivery had a success rate of 12,490 of 16,915 (74%) compared with 648 of 975 (66%) in women with multiple prior cesarean deliveries (P < .001). The trial of labor success rates were 584 of 871 (67%) for two prior, 53 of 84 (63%) for three prior, and 11 of 20 (55%) for four prior cesarean deliveries (P < .001).
Uterine rupture occurred in 9 (0.9%) cases with multiple prior cesarean compared with 115 (0.7%) with a single prior operation; the difference was not statistically significant (P = .37) (Table 2). The rates of hysterectomy and transfusion were significantly higher in the multiple prior cesarean group. A composite of maternal morbidity consisting of uterine rupture, endometritis, hysterectomy, transfusion, thromboembolic disease, and operative injury revealed an increased risk for women with multiple prior cesarean deliveries compared with those with single prior cesarean delivery (P = .001). A multivariable model controlling for age, race, marital status, tobacco use, insurance status, birth weight, and prior vaginal delivery confirmed an increased risk for maternal morbidity in the multiple prior cesarean delivery group (odds ratio [OR] 1.35, 95% confidence interval [CI] 1.031.75). Among perinatal outcomes, the frequency of both term intrapartum stillbirth and term neonatal death were not statistically different among comparison groups. There were no cases of hypoxic ischemic encephalopathy in term infants of women with multiple prior cesarean delivery undergoing trial of labor compared with 12 such cases in women with a single prior cesarean delivery.
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Risk factors for uterine rupture are presented in Table 3. Oxytocin augmentation, induction of labor, epidural anesthesia, and less than a 2-year interval from previous cesarean delivery were associated with higher rates of uterine rupture. Both prior vaginal delivery and prior successful VBAC were associated with a lower risk for this complication. Three multivariable models were constructed to control for confounding variables associated with uterine rupture (Table 4). In all adjusted models, multiple prior cesarean delivery was not associated with an increased risk for uterine rupture. Oxytocin augmentation and induction remained significant risk factors, whereas a history of vaginal delivery remained protective against the risk for uterine rupture in two of the models. The rate of uterine rupture in women with multiple prior cesarean delivery and a prior vaginal delivery was 5 in 497 (1%) compared with 4 in 470 (0.85%) in women without a prior vaginal birth (P = 1.0).
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Demographic information and obstetric features of women with multiple prior cesarean deliveries undergoing trial of labor versus elective repeat cesarean delivery is presented in Table 5. Women undergoing trial of labor were younger and more likely to be unmarried, African American, tobacco users, and receiving public assistance. Lower birth weight, earlier gestational age, history of vaginal delivery, and VBAC were more common in those undergoing trial of labor. Maternal morbidity, consisting primarily of uterine rupture and blood transfusion, was more commonly observed in women undergoing trial of labor (Table 6). Multivariable analysis controlling for age, race, marital status, tobacco use, insurance status, birth weight, and prior vaginal delivery confirmed an increased risk for a composite of maternal morbidity with trial of labor (OR 1.41, 95% CI 1.021.93). There were no significant differences in perinatal outcomes among term infants of women undergoing trial of labor versus elective repeat cesarean delivery.
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| DISCUSSION |
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Our study also demonstrates that perinatal outcomes for this population are comparable to those observed in women with one prior cesarean delivery attempting VBAC. This information is important for counseling women regarding their options for childbirth after multiple prior cesarean deliveries.
There are a few large-scale studies addressing safety and efficacy after trial of labor after multiple prior cesarean deliveries. Previous studies have been primarily retrospective, and most are within single institutions encompassing long study periods.4,68 Our study is unique in its large-scale, multicenter, prospective design with trained obstetric research staff using standardized definitions.3 In designing this study, we specifically planned for a sufficient sample size to address the question of whether multiple prior cesarean deliveries are associated with an increased rate of uterine rupture in women undergoing trial of labor.
In the largest series to date, Miller and colleagues4 reported their 10-year experience with 1,827 women with multiple prior cesarean deliveries undergoing trial of labor. Uterine rupture occurred in 1.7% of women with more than one prior cesarean compared with 0.6% in women with single prior operation (OR 3.06, 95% CI 1.954.79). This analysis, however, did not control for potential confounding variables, including labor induction and prior obstetric history. Caughey and colleagues5 conducted a single-center retrospective review from a 12-year period in which the rate of uterine rupture was 3.7% (5/134) in women with 2 prior cesareans compared with 0.8% (31/3,757) in women with one previous uterine scar. These authors controlled for labor characteristics and obstetric history and reported that women with two scars were 4.8 times more likely to experience uterine rupture during trial of labor than women with one scar (OR 4.8, 95% CI 1.813.2). Most recently, in a large scale multicenter retrospective study, Macones et al6 reported a smaller, but increased rate of uterine rupture of 1.8% (20/1,082) in women with 2 prior cesareans versus 0.9% (113/12,535) in women with one previous cesarean delivery (adjusted OR 2.30, 95% CI 1.373.85). Interestingly, in a subsequent case-controlled analysis from the same cohort, these authors did not confirm multiple prior cesareans as an independent historical risk factor for uterine rupture with trial of labor (adjusted OR 1.45, 95% CI 0.643.27).9 Thus, our findings contrast with most prior reports and Macones observation of a small, but statistically significant increased risk of uterine rupture for women with multiple prior cesarean deliveries.6 We powered our study to detect a RR of 2.53.0, so that it remains possible that the increasing risk for uterine rupture, if present, may be closer to a two-fold difference as reported by Macones. Alternatively, differences in population characteristics and obstetric practice may account for the discordant findings among studies. In our study, the trial-of-labor rate for women with multiple prior operations was 9.2%, compared with 27.2% in Macones report and 49.0% in Millers study. Caughey and colleagues did not report their trial-of-labor rate for women in their 12-year data analysis. A potentially more selective approach for choosing candidates for trial of labor over the last few years might be associated with a reduced risk for uterine rupture present in our study population.
Our report provides a large-scale, prospective comparison of maternal outcomes in women with multiple prior operations undergoing trial of labor versus those having elective repeat cesarean. This comparison addresses the clinically relevant question as to the preferred mode of delivery for this population of women. Our study and the work of Macones and colleagues demonstrate that uterine rupture is the complication with the greatest risk attributable to trial of labor. Our finding of an increased risk for an adjusted composite of maternal morbidity with trial of labor (OR 1.41) confirms Macones observation (OR 2.26).6 Both studies thus reveal a relatively low level of increased risk that will likely be acceptable to many women considering VBAC. Although our study also provides perinatal outcome data demonstrating no apparent increased risk with trial of labor compared with elective repeat cesarean delivery after multiple prior cesareans, we recognize that the population size is insufficient to address differences in these outcomes. It is, however, likely that a larger study population would demonstrate a small but increased risk for adverse perinatal outcomes in women undergoing trial of labor as we have demonstrated in the combined cohort of women with single and multiple prior operations.3
We have confirmed that the majority of women with multiple prior cesarean deliveries undergoing trial of labor can expect to achieve a successful vaginal birth. Our reported success rate of 66% is, however, significantly lower than for women with one prior cesarean delivery (73%). This difference has been consistently reported in other studies.4,5 This finding does contrast with Macones observation of similar success rates (75.5% versus 74.6%) between study groups. Both our study and Macones analysis reveal high rates of prior vaginal delivery in women with multiple prior cesarean delivery attempting trial of labor, yet these rates were not higher than in women with single prior operation. It is possible that our finding, and that of others, of lower VBAC success with multiple prior cesarean deliveries may be explained by differences in study population characteristics that affect labor success.10
Our study does have several limitations. Women with multiple prior cesarean deliveries who undergo counseling and then elect a trial of labor have characteristics that are different from both women with a single prior operation and those who elect a repeat operation. We attempted to control for these differences in our analysis, but different approaches to labor management in particular are likely to be present among comparison groups. Our study does not provide long-term outcome data, which is particularly relevant for women undergoing multiple repeat operations who have the associated risk for hemorrhage from accreta and hysterectomy. We also recognize that our data collection process did not provide information regarding certain potential risk factors associated with uterine rupture, such as prior uterine closure technique. Nonetheless, we did attempt to control for most recognized factors and, in doing so, confirmed an association between oxytocin augmentation and induction with uterine rupture as well as the protective effect of prior vaginal delivery.3,11
In summary, it appears that any increased risk for uterine rupture in women with multiple prior cesarean deliveries attempting VBAC must be statistically small. As with women who have a single prior cesarean, this risk may be modified by clinical factors such as the need for induction and history of vaginal delivery. However, a requirement that a history of vaginal delivery be present in women with multiple prior cesarean deliveries to be considered candidates for trial of labor seems unwarranted given the apparent level of risk for uterine rupture and adverse outcomes in this population. Moreover, a comparison of outcomes after trial of labor in women with multiple prior cesarean versus those undergoing elective repeat operation indicates that both options should remain available for eligible women.
| APPENDIX |
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The Ohio State University, Columbus, OH: J. Iams, F. Johnson, S. Meadows, H. Walker
University of Alabama at Birmingham, Birmingham, AL: D. Rouse, A. Northen, S. Tate
University of Texas Southwestern Medical Center, Dallas, TX: K. Leveno, J. Mc Campbell, D. Bradford
University of Utah, Salt Lake City, UT: M. Belfort, F. Porter, B. Oshiro, K. Anderson, A. Guzman
University of Chicago, Chicago, IL: J. Hibbard, P. Jones, M. Ramos-Brinson, M. Moran, D. Scott
University of Pittsburgh, Pittsburgh, PA: K. Lain, M. Cotroneo, D. Fischer, M. Luce
Wake Forest University, Winston-Salem, NC: P. Meis, M. Swain, C. Moorefield, K. Lanier, L. Steele
Thomas Jefferson University, Philadelphia, PA: A. Sciscione, M. DiVito, M. Talucci, M. Pollock
Wayne State University, Detroit, MI: M. Dombrowski, G. Norman, A. Millinder, C. Sudz, B. Steffy
University of Cincinnati, Cincinnati, OH: T. Siddiqi, H. How, N. Elder
Columbia University, New York, NY: F. Malone, M. DAlton, V. Pemberton, V. Carmona, H. Husami
Brown University, Providence, RI: H. Silver, J. Tillinghast, D. Catlow, D. Allard
Northwestern University, Chicago, IL: M. Socol, D. Gradishar, G. Mallett
University of Miami, Miami, FL: G. Burkett, J. Gilles, J. Potter, F. Doyle, S. Chandler
University of Tennessee, Memphis, TN: W. Mabie, R. Ramsey
University of Texas Health Science Center at San Antonio, San Antonio, TX: D. Conway, S. Barker, M. Rodriguez
University of North Carolina at Chapel Hill, Chapel Hill, NC: K. Moise, K. Dorman, S. Brody, J. Mitchell
University of Texas Health Science Center at Houston, Houston, TX: L. Gilstrap, M. Day, M. Kerr, E. Gildersleeve
Case Western Reserve University, Cleveland, OH: P. Catalano, C. Milluzzi, B. Silvers, C. Santori
The George Washington University Biostatistics Center, Washington, DC: S. Gilbert, H. Juliussen-Stevenson, M. Fischer
National Institute of Child Health and Human Development, Bethesda, MD: D. McNellis, K. Howell, S. Pagliaro
| Footnotes |
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* For members of the NICHD Maternal-fetal Medicine Units Network, see the Appendix.
Supported by grants From the National Institute of Child Health and Human Development (HD21410, HD21414, HD27860, HD27861, HD27869, HD27905, HD27915, HD27917, HD34116, HD34122, HD34136, HD34208, HD34210, HD40500, HD40485, HD40544, HD40545, HD40560, HD40512, and HD36801).
The following core committee members participated in protocol/data management and statistical analysis: Sharon Gilbert, MS; and protocol development and coordination between clinical research centers: Frances Johnson, RN, and Julia McCampbell, RN.
Corresponding author: Mark B. Landon, MD, the Ohio State University College of Medicine and Public Health, 1654 Upham Drive, Means Hall 5th Floor, Columbus, OH 43210-1228; e-mail: landon.1{at}osu.edu. ![]()
doi:10.1097/01.AOG.0000224694.32531.f3
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