Doi:10.1016/j.ajog.2004.02.035

American Journal of Obstetrics and Gynecology (2004) 190, 1476e8 Risk of uterine rupture in labor induction of patientswith prior cesarean section: An inner city hospitalexperience Department of Gynecology and Obstetrics, Emory University at Grady Healthcare System, Atlanta, Ga Received for publication September 10, 2003; revised December 31, 2003; accepted February 4, 2004 –––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Objective: This study was undertaken to determine the risk of uterine rupture in patients induced with oxytocin or misoprostol after 1 or more previous cesarean sections.
Study design: Patients with 1 or more previous cesarean sections who delivered after 28 weeks’ gestation between 1996 and 2002 were identified by database. Among 3533 total patients, rates of uterine rupture were compared among 4 groups: oxytocin induction (n = 430), misoprostol in- duction (n = 142), spontaneous labor (n = 2523), and repeat cesarean section without labor(n = 438). Statistical analysis included c2 test, Fisher exact test, unpaired t test, and Mantel-Haenszel test.
Results: Rate of rupture was increased in all inductions compared with that of the spontaneouslabor group. Among patients with 1 prior cesarean, rupture rates with misoprostol and oxytocininduction were 0.8% and 1.1%, respectively.
Conclusion: Induction of labor with oxytocin or misoprostol is associated with a higher rate ofuterine rupture compared with those who deliver after spontaneous labor. After 1 prior cesarean,rupture rate with misoprostol induction is not increased compared with oxytocin induction.
Ó 2004 Elsevier Inc. All rights reserved.
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– The risk of uterine rupture in an attempted vaginal birth after cesarean section is reported to range from0.5% to 1.0%.Although rare, uterine rupture has A database was used to identify patients delivering at 28 played a role in shaping obstetric practice, causing some weeks or greater between January 1996 and July 2002 to question the entire practice of trial of labor.
whose history included previous cesarean section. In- Recent studies show an association between labor in- complete records were excluded. Information was ex- duction and uterine ruptureHowever, systematic tracted on race, maternal age, parity, gestational age data on misoprostol as an induction agent are lacking.
at delivery, mode of delivery, presentation, infant Studies have also been limited to patients with 1 prior weight, induction agent, previous uterine scar, number cesarean section. This study aimed to determine the risk and type of prior cesarean sections.
of uterine rupture in patients undergoing induction of Four study groups were defined: (1) repeat cesarean labor with misoprostol or oxytocin after 1 or more pre- without labor, (2) spontaneous labor, (3) oxytocin in- duction, and (4) misoprostol induction.
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doi:10.1016/j.ajog.2004.02.035 Risk of uterine rupture was increased in all induc- Patients by number and type of previous cesarean tions compared with women delivered by cesarean sec- tion without labor (OR 5.41 [95% CI 1.0-40.34]). The rupture risks were similar between oxytocin (OR 5.14 [95% CI 0.59-116.8]) and misoprostol (OR 6.24 [95% CI 0.44-175.2]). When inductions were compared with the spontaneous labor group, rupture risk was also increased but not statistically significant (OR 2.68 [95% CI 0.81- 8.39]). Laboring women, spontaneous or induced, were more likely to have uterine rupture com- * Unidentified patients were not included in analysis that required pared with women undergoing cesarean section without information about cesarean number or scar type.
With respect to the number of previous cesarean de- liveries, rupture rates in patients with multiple prior Induction agents were selected by individual practi- cesarean sections were higher than those with 1 prior tioners. General practice involved the use of misoprostol cesarean, although not statistically significant. In the in patients with unfavorable cervix. However, misopros- spontaneous labor group, the rupture rate was 0.4% tol use varied throughout the study period. Similarly, (7/2000) in patients with 1 prior cesarean, compared the use of oxytocin with respect to cervical ripeness var- with 0.8% (4/523) for those with more than 1 cesarean ied with the availability of other agents. Oxytocin induc- section; in the oxytocin group, the rupture rates were tion was distinguished from augmentation by database 1.1% (4/376) and 1.9% (1/54), respectively; in the miso- variables. Information was validated by review of med- prostol group, rupture rates were 0.8% (1/123) and Uterine rupture was defined as uterine scar separa- Patients with a prior low transverse scar had a similar tion associated with abnormal fetal heart rate tracing, rupture rate compared with those with unknown scar extrusion of fetal parts, or hemorrhage. Operative re- (0.6% and 0.5%, respectively). No uterine ruptures oc- ports were reviewed; cases that failed to meet criteria curred in patients with classical or low vertical scars.
were reclassified as uterine dehiscence.
Statistical analysis included c2 test and Fisher exact test for categorical variables, unpaired t test for contin-uous variables, and Mantel-Haenszel test to calculate odds ratios (ORs). Approval was obtained from the In- Our study demonstrated a higher rate of uterine rupture in patients undergoing induction of labor after previouscesarean section when compared with that in spontane-ous labor. The overall rupture rate was consistent withprevious studiThe rate of rupture in all induced pa- tients was similar to a prior study,but lower than the2.3% in Zelop et al.Our sample differed with the inclu- A total 29,919 patients delivered at our institution dur- sion of a misoprostol group and patients with multiple ing the study period; of patients with previous cesarean sections, 3,659 delivered at 28 weeks or greater. After ex- This study is the first to evaluate rupture risk of pa- clusions 3,533 patients remained in the study: 438 in tients undergoing misoprostol induced trial of labor the elective cesarean group; 2,523 in the spontaneous la- compared with spontaneous labor or no labor. Prior bor group; 430 in the oxytocin group; 142 in the miso- studies have been case reports that included asymptom- prostol group. displays the patients by number atic dehiscences, or did not include misoprostol as a single of previous cesarean section and scar type. The study study group.The largest study lacked data specific to groups were similar in race, maternal age, number of misoprostol use and instead reported a rate of 2.3% for prior cesarean sections, and infant birth weight. Demo- all prostaglandin inductioUltimately, misoprostol graphics between ruptures and nonruptures were also use in patients with scarred uteri was discontinued with- out an estimate of uterine rupture risk.Our rupture rate The overall rate of rupture was 0.5% (19/3533). For for misoprostol induction in patients with 1 prior cesar- all inductions the rate was 1.2% (7/572); rupture rates ean section was similar to that for oxytocin induction.
in the oxytocin and misoprostol groups were 1.2% (5/ Studies of oxytocin induction in vaginal birth after 430) and 1.4% (2/142), respectively. Rupture occurred cesarean sections have conflicting resulZelop et in 0.2% (1/438) of the repeat cesarean group, and found a 4-fold increase risk of rupture in patients receiv- 0.4% (11/2523) in the spontaneous labor group.
ing oxytocin for induction. Our study showed an increased risk of rupture with oxytocin, but not to the Past induction studies have been limited to patients 1. Caughey AB, Shipp TD, Repke JT, Zeion CM, Cohen A, with 1 prior cesarean section; ours is the first to include Lieberman E. Rate of uterine rupture during a trial of labor inwomen with one or two prior cesarean deliveries. Am J Obstet patients with multiple cesarean sections. Although not statistically significant, rupture rates in patients with 2. Ravasia DJ, Wood SL, Pollard JK. Uterine rupture during induced multiple cesarean sections were consistently higher, sim- trial of labor among women with previous cesarean delivery. Am J ilar to studies that did not focus on induction.
Sample size was a limitation of this study. Also, exact 3. Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. Risk of uterine rupture during labor among women with a prior cesarean dosages of induction agents could not be verified. Ante- delivery. N Engl J Med 2001;345:3-8.
partum complications were not controlled for; however, 4. Phelan JP. VBAC: Time to reconsider? OBG Management 1996; a prior study found this was not a significant factor.In addition we did not control for factors that may be im- 5. Zelop CM, Shipp TD, Repke JT, Cohen A, Caughey AB, portant in rupture such as interdelivery interval and en- Lieberman E. Uterine rupture during induced or augmented laborin gravid women with one prior cesarean delivery. Am J Obstet To conclude, our study showed an increased uterine 6. Wing DA, Lovett K, Paul RH. Disruption of prior uterine incision rupture rate in patients undergoing induction compared following misoprostol for labor induction in women with previous with patients in spontaneous labor, which seemed to be cesarean delivery. Obstet Gynecol 1998;91:828-30.
further increased in patients with multiple prior cesarean 7. Plaut MM, Schwartz ML, Lubarsky SL. Uterine rupture associated with the use of misoprostol in the gravid patient with a previous sections. Our data imply that rupture rate with miso- cesarean section. Am J Obstet Gynecol 1999;180:1535-42.
prostol is similar to that with oxytocin induction. Miso- 8. American College of Obstetricians and Gynecologists. Induction of prostol will likely never be used again in patients with labor for vaginal birth after cesarean delivery. Washington (DC): uterine scarring, but it is possible that the risk of rupture The College; 2002 ACOG Committee Opinion No. 271.
is not increased compared with agents such as oxytocin 9. Flamm BL, Goings JR, Fuelberth NJ, Fischermann E, Jones C, Hersh E. Oxytocin during labor after previous cesarean section: that continue to be used in these patients.
results of a multicenter study. Obstet Gynecol 1987;70:709-12.

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