Interdelivery interval and risk of symptomatic uterine rupture

OBJECTIVE: To relate interdelivery interval to risk of uterine rupture during a trial of labor after prior cesarean delivery. METHODS: We reviewed the medical records of all women who had a trial of labor after cesarean delivery over 12 years (July 1984 to June 1996). Analysis was limited to women with only one prior cesarean delivery and no prior vaginal deliveries who delivered term singletons and whose medical records included the month and year of the prior delivery. The time in months between the prior cesarean delivery and the index trial of labor was calculated, and the women were divided accordingly to permit comparison with respect to symptomatic uterine rupture. RESULTS: Two thousand four hundred nine women had trials of labor after one prior cesarean delivery and had complete data from the medical records. There were 29 uterine ruptures (1.2%) in the population. For interdelivery intervals up to 18 months, the uterine rupture rate was 2.25% (seven of 311) compared with 1.05% (22 of 2098) with intervals of 19 months or longer (P =.07). Multiple logistic regression was used to assess the risk of uterine rupture according to interdelivery interval while controlling for maternal age, public assistance, length of labor, gestational age at least 41 weeks, and oxytocin use. Women with interdelivery intervals of up to 18 months were three times as likely (95% confidence interval, 1.2, 7.2) to have symptomatic uterine rupture. CONCLUSION: Interdelivery intervals of up to 18 months were associated with increased risk of symptomatic uterine rupture during a trial of labor after cesarean delivery compared with that for longer interdelivery intervals.     

Uterine rupture during induced or augmented labor in gravid women with one prior cesarean delivery.

OBJECTIVE: Our purpose was to examine the risk of uterine rupture during induction or augmentation of labor in gravid women with 1 prior cesarean delivery. STUDY DESIGN: The medical records of all gravid women with history of cesarean delivery who attempted a trial of labor during a 12-year period at a single center were reviewed. The current analysis was limited to women at term with 1 prior cesarean delivery and no other deliveries. The rate of uterine rupture in gravid women within that group undergoing induction was compared with that in spontaneously laboring women. The association of oxytocin induction, oxytocin augmentation, and use of prostaglandin E(2) gel with uterine rupture was determined. Logistic regression analysis was used to examine these associations, with control for confounding factors. RESULTS: Of 2774 women in the analysis, 2214 had spontaneous onset of labor and 560 women had labor induced with oxytocin or prostaglandin E(2) gel. The overall rate of rupture among all patients with induction of labor was 2.3%, in comparison with 0.7% among women with spontaneous labor (P =.001). Among 1072 patients receiving oxytocin augmentation, the rate of uterine rupture was 1.0%, in comparison with 0.4% in nonaugmented, spontaneously laboring patients (P =.1). In a logistic regression model with control for birth weight, use of epidural, duration of labor, maternal age, year of delivery, and years since last birth, induction with oxytocin was associated with a 4.6-fold increased risk of uterine rupture compared with no oxytocin use (95% confidence interval, 1.5-14.1). In that model, augmentation with oxytocin was associated with an odds ratio of 2.3 (95% confidence interval, 0.8-7.0), and use of prostaglandin E(2) gel was associated with an odds ratio of 3.2 (95% confidence interval, 0.9-10.9). These differences were not statistically significant. CONCLUSION: Induction of labor with oxytocin is associated with an increased rate of uterine rupture in gravid women with 1 prior uterine scar in comparison with the rate in spontaneously laboring women. Although the rate of uterine rupture was not statistically increased during oxytocin augmentation, use of oxytocin in such cases should proceed with caution.     

The association of maternal age and symptomatic uterine rupture during a trial of labor after prior cesarean delivery

OBJECTIVE: To estimate whether maternal age is associated with a symptomatic uterine rupture during a trial of labor after prior cesarean delivery. METHODS: We retrospectively reviewed the medical records of all patients undergoing a trial of labor after prior cesarean delivery over a 12-year period. We analyzed the labors of women with one prior cesarean and no prior vaginal deliveries. The uterine rupture rate was determined with respect to maternal age. Multiple logistic regression was used to control for potential confounding variables. RESULTS: Overall, 32 (1.1%) uterine ruptures occurred among 3015 women. For women younger than 30 years, the risk of uterine rupture was 0.5%, and for those women aged at least 30 years, the risk of uterine rupture was 1.4% (P =.02). Controlling for birth weight, induction, augmentation, and interdelivery interval, the odds ratio for symptomatic uterine rupture for women aged at least 30 years compared with those less than 30 years was 3.2 (95% confidence interval 1.2, 8.4). CONCLUSION: Women aged 30 years or older have a greater risk of uterine rupture as compared with women younger than 30 years.     

Previous preterm cesarean delivery and risk of subsequent uterine rupture

OBJECTIVE: To determine if women with a history of a previous preterm cesarean delivery experienced an increased risk of subsequent uterine rupture compared with women who had a previous nonclassic term cesarean delivery. METHODS: A prospective observational study was performed in singleton gestations that had a previous nonclassic cesarean delivery from 1999 to 2002. Women with a history of a previous preterm cesarean delivery were compared with women who had a previous term cesarean delivery. Women who had both a preterm and term cesarean delivery were included in the preterm group. RESULTS: A prior preterm cesarean delivery was significantly associated with an increased risk of subsequent uterine rupture (0.58% compared with 0.28%, P<.001). When women who had a subsequent elective cesarean delivery were removed (remaining n=26,454) women with a previous preterm cesarean delivery were still significantly more likely to sustain a uterine rupture (0.79% compared with 0.46%, P=.001). However, when only women who had a subsequent trial of labor were included, there was still an absolute increased risk of uterine rupture, but it was not statistically significant (1.00% compared with 0.68%, P=.081). In a multivariable analysis controlling for confounding variables (oxytocin use, two or more previous cesarean deliveries, a cesarean delivery within the past 2 years, and preterm delivery in the current pregnancy), patients with a previous preterm cesarean delivery remained at an increased risk of subsequent uterine rupture (P=.043, odds ratio 1.6, 95% confidence interval 1.01-2.50) compared with women with previous term cesarean delivery. CONCLUSION: Women who have had a previous preterm cesarean delivery are at a minimally increased risk for uterine rupture in a subsequent pregnancy when compared with women who have had previous term cesarean deliveries.     

Effect of previous vaginal delivery on the risk of uterine rupture during a subsequent trial of labor

OBJECTIVE: We examined the effect of prior vaginal delivery on the risk of uterine rupture in pregnant women undergoing a trial of labor after prior cesarean delivery. STUDY DESIGN: The medical records of all pregnant women with a history of cesarean delivery who attempted a trial of labor during a 12-year period at a single center were reviewed. For the current analysis, the study population was limited to term pregnancies. The effect of previous vaginal delivery on the risk of uterine rupture during a subsequent trial of labor was evaluated. Separate analyses were performed for women with a single previous cesarean delivery and for those with >1 prior cesarean delivery. For each of these subgroups, the rate of uterine rupture among women who had > or =1 prior vaginal delivery was compared with the rate among women with no prior vaginal delivery. Logistic regression analysis was used to examine the associations with control for confounding factors. RESULTS: Of 3783 women with 1 prior scar, 1021 (27.0%) also had > or =1 prior vaginal delivery. During a subsequent trial of labor, the rate of uterine rupture was 1.1% among pregnant women without prior vaginal delivery and 0.2% among pregnant women with prior vaginal delivery (P =.01). Logistic regression analysis controlling for duration of labor, induction, birth weight, maternal age, year of birth, epidural analgesia, and oxytocin augmentation indicated that, among women with a single scar, those with a prior vaginal delivery had a risk of uterine rupture that was one fifth that of women without a previous vaginal delivery (odds ratio, 0.2; 95% confidence interval, 0.04-0.8). In the group of 143 pregnant women with >1 previous cesarean delivery, women with a prior vaginal delivery had a somewhat lower risk of uterine rupture (3.9% vs 2.5%; adjusted odds ratio, 0.6; 95% confidence interval, 0.01-6.7). This difference was not statistically significant. CONCLUSION: Among women with 1 prior cesarean delivery undergoing a subsequent trial of labor, those with a prior vaginal delivery were at substantially lower risk of uterine rupture than women without a previous vaginal delivery.     

Risk of uterine rupture with a trial of labor in women with multiple and single prior cesarean delivery

OBJECTIVE: To determine whether the risk for uterine rupture is increased in women attempting vaginal birth after multiple cesarean deliveries. 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 1.02-1.93). 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.     

Post-cesarean delivery fever and uterine rupture in a subsequent trial of labor

OBJECTIVE: To evaluate the association of uterine rupture during a trial of labor after cesarean with postpartum fever after the prior cesarean delivery. METHODS: We conducted a nested, case-control study in a cohort of all women undergoing a trial of labor after cesarean over a 12-year period in a single tertiary care institution. The current study was limited to all women undergoing a trial of labor after cesarean at term with a symptomatic uterine rupture and who also had their prior cesarean at the same institution. Four controls, who all had their prior cesarean at the same institution, were matched to each case by year of delivery, number of prior cesareans, prior vaginal delivery, and induction in the index pregnancy. Medical records were reviewed for maximum postpartum temperature for the previous cesarean. Fever was defined as a temperature above 38C. Conditional logistic regression analysis was performed taking into account potential confounding factors. RESULTS: There were 21 cases of uterine rupture included in the analysis. The rate of fever following the prior cesarean was 38% (8/21) among the cases, and 15% (13/84) in the controls, P =.03. Multiple logistic regression analysis examining the association of uterine rupture and postpartum fever adjusting for confounders revealed an odds ratio of 4.0, 95% confidence interval 1.0, 15.5. CONCLUSION: Postpartum fever after cesarean delivery is associated with an increased risk of uterine rupture during a subsequent trial of labor.     

Uterine rupture associated with misoprostol labor induction in women with previous cesarean delivery

OBJECTIVE: To review our experience with uterine rupture in patients undergoing a trial of labor with a history of previous cesarean delivery in which labor was induced with misoprostol. STUDY DESIGN: A retrospective chart review was used to select patients who underwent induction of labor with misoprostol during the period from February 1999 to June 2002. Women with a history of cesarean delivery were retrospectively compared with those without uterine scarring. RESULTS: Uterine rupture occurred in 4 of 41 patients with previous cesarean delivery who had labor induced with misoprostol. The rate of uterine rupture (9.7%) was significantly higher in patients with a previous cesarean delivery (P<0.001). No uterine rupture occurred in 50 patients without uterine scarring. Women with a history of cesarean delivery were more likely to have oxytocin augmentation than those without uterine scarring (41% versus 20%; P=0.037). CONCLUSION: Misoprostol induction of labor increases the risk of uterine rupture in women with a history of cesarean delivery.     

Outcomes of trial of labor following previous cesarean delivery among women with fetuses weighing >4000 g

OBJECTIVE: To compare outcomes at term of a trial of labor in women with previous cesarean delivery who delivered neonates weighing > 4000 g versus women with those weighing < or = 4000 g. STUDY DESIGN: We reviewed medical records for all women undergoing a trial of labor after prior cesarean delivery during a 12-year period. The current analysis was limited to women at term with one prior cesarean and no other deliveries. The rates of cesarean delivery and symptomatic uterine rupture for women with infants weighing > 4000 g were compared to the rates for women with infants weighing < or = 4000 g. Logistic regression was used to control for the potential confounding by use of epidural, maternal age, labor induction, labor augmentation, indication for previous cesarean, type of uterine hysterotomy, year of delivery, receiving public assistance, and maternal race. Adjusted odds ratios and 95% confidence intervals were calculated. RESULTS: Of 2749 women, 13% (365) had infants with birth weights > 4000 g. Cesarean delivery rate associated with birth weights < or = 4000 g was 29% versus 40% for those with birth weights > 4000 g (P = .001). With use of logistic regression, we found that birth weight > 4000 g was associated with a 1.7-fold increase in risk of cesarean delivery (95% CI, 1.3-2.2). The rate of uterine rupture for women with infants weighing < or = 4000 g was 1.0% versus a 1.6% rate for those with infants weighing > 4000 g (P = .24). Although the logistic regression analysis revealed a somewhat higher rate of uterine rupture associated with birth weights of > 4000 g (adjusted OR, 1.6; 95% CI, 0.7-4.1), this difference was not statistically significant. The rate of uterine rupture was 2.4% for women with infants weighing > 4250 g, but this rate did not differ significantly from the rate of uterine rupture associated with birth weights < or = 4250 g (P = .1). CONCLUSION: A trial of labor after previous cesarean delivery may be a reasonable clinical option for pregnant women with suspected birth weights of > 4000 g, given that the rate of uterine rupture associated with these weights does not appear to be substantially increased when compared to lower birth weights. However, some caution may apply when considering a trial of labor in women with infants weighing > 4250 g. In these women with infants weighing > 4000 g, the likelihood of successful vaginal delivery, although lower than for neonates weighing < or = 4000 g, is still 60%.     

Oxytocin dose and the risk of uterine rupture in trial of labor after cesarean

OBJECTIVE: To examine the association between uterine rupture and oxytocin use in trial of labor after cesarean. METHODS: A case-control study was performed. Cases were all women with uterine ruptures who received oxytocin during a trial of labor after a single cesarean delivery within a 12-year period (n = 24). Four controls undergoing trial of labor after a single cesarean delivery were matched to each case by 500 g birth weight category, year of birth, and by induction or augmentation (n = 96). The study had an 80% power to detect a 40% increase in oxytocin duration or a 65% increase in total oxytocin dose. RESULTS: No significant differences were seen in initial oxytocin dose, maximum dose, or time to maximum dose. Although women with uterine ruptures had higher exposure to oxytocin as measured by mean total oxytocin dose (544 mU higher) and oxytocin duration (54 minutes longer), these differences were not statistically significant. Women with uterine rupture who received oxytocin were more likely to have experienced an episode of uterine hyperstimulation (37.5% compared with 20.8%, P =.05). However, the positive predictive value of hyperstimulation for uterine rupture was only 2.8%. CONCLUSION: Although no significant differences in exposure to oxytocin were detected between cases of uterine rupture and controls, the rarity of uterine rupture limited our power to detect small differences in exposure. In women receiving oxytocin, uterine rupture is associated with an increase in uterine hyperstimulation, but the clinical value of hyperstimulation for predicting uterine rupture is limited.     

Vaginal birth after cesarean and uterine rupture rates in California

OBJECTIVE: To describe attempted and successful vaginal birth after cesarean (VBAC) rates and uterine rupture rates for women with and without prior cesareans, and compare delivery outcomes in hospitals with different attempted VBAC rates. METHODS: We used California hospital discharge summary data for 1995 to calculate attempted and successful VBAC rates and uterine rupture rates. We used multivariate logistic regression models to evaluate and adjust for age, ethnicity, and payment source. We report the relative risk (RR), attributable fraction, and 95% confidence intervals (CIs) for uterine rupture. RESULTS: There were 536,785 delivery discharges during 1995. The cesarean rate was 20.8%, and 12.5% of women had histories of cesareans. Of women with histories of cesareans, 61.4% attempted VBAC and 34.8% were successful. There were 392 uterine ruptures (0.07%). Women with prior cesareans were 16.98 (95% CI 13.51, 21.43) times more likely to experience uterine rupture, attributable fraction 66% (95% CI 60%, 73%). Among women with prior cesareans, those who attempted VBAC were 1.88 (95% CI 1.45, 2.44) times as likely to have uterine rupture, attributable fraction 34% (95% CI 21%, 46%). Women who delivered in hospitals with high attempted VBAC rates were less likely to have cesarean deliveries, more likely to have successful VBACs, and more likely to experience uterine ruptures. CONCLUSION: Uterine rupture occurs at a low rate in women with and without prior cesarean delivery. Risk of rupture is increased among women with prior cesarean delivery and among those who attempt VBAC.     

Association between prior vaginal birth after cesarean and subsequent labor outcome

Objective: To estimate the effect of prior successful vaginal birth after cesarean (VBAC) on the rate of uterine rupture and delivery outcome in women undergoing labor after cesarean.

Methods: A retrospective cohort study of all women attempting labor after cesarean delivery in a university-affiliated tertiary-hospital (2007–2014) was conducted. Study group included women attempting vaginal delivery with a history of cesarean delivery and at least one prior VBAC. Control group included women attempting first vaginal delivery following cesarean delivery. Primary outcome was defined as the rate of uterine rupture. Secondary outcomes were delivery and maternal outcomes.

Results: Of 62,463 deliveries during the study period, 3256 met inclusion criteria. One thousand two hundred and eleven women had VBAC prior to the index labor and 2045 underwent their first labor after cesarean. Women in the study group had a significantly lower rate of uterine rupture 9 (0.7%) in respect to control 33 (1.6%), p?=?.036, and had a higher rate of successful vaginal birth (96 vs. 84.9%, p?p?=?.04).

Conclusions: In women attempting labor after cesarean, prior VBAC appears to be associated with lower rate of uterine rupture and higher rate of successful vaginal birth.     

Trial of labor after 40 weeks' gestation in women with prior cesarean

OBJECTIVE: To compare outcomes in women with prior cesareans delivering at or before 40 weeks' gestation with those delivering after 40 weeks. METHODS: We reviewed labor outcomes over 12 years at one institution for women with one prior cesarean and no other deliveries who had a trial of labor at term. We analyzed the rates of symptomatic uterine rupture and cesarean for term deliveries before or after 40 weeks and stratified for spontaneous and induced labor. Potential confounding by birth weight was controlled using logistic regression. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated. RESULTS: Of 2775 women with one prior scar and no other deliveries, 1504 delivered at or before 40 weeks and 1271 delivered after 40 weeks. For spontaneous labor, rupture rate at or before 40 weeks was 0.5% compared with 1.0% after 40 weeks (P =.2, adjusted OR 2.1, CI 0.7, 5.7). For induced labor, uterine rupture rates were 2.1% at or before 40 weeks and 2.6% after 40 weeks (P =.7, adjusted OR 1.1, CI 0.4, 3.4). For spontaneous labor, rate of cesareans during subsequent trials of labor at or before 40 weeks was 25% compared with 33.5% after 40 weeks (P =.001, adjusted OR 1.5, CI 1.2, 1.8). For induced labor, rate of cesareans during subsequent trials of labor at or before 40 weeks was 33.8% compared with 43% after 40 weeks (P =.03, adjusted OR 1.5, CI 1.1, 2.2). CONCLUSION: The risk of uterine rupture does not increase substantially after 40 weeks but is increased with induction of labor regardless of gestational age. Because spontaneous labor after 40 weeks is associated with a cesarean rate similar to that following induced labor before 40 weeks, awaiting spontaneous labor after 40 weeks does not decrease the likelihood of successful vaginal delivery.     

Risk of uterine rupture and adverse perinatal outcome at term after cesarean delivery

OBJECTIVE: Current information on the risk of uterine rupture after cesarean delivery has generally compared the risk after trial of labor to that occurring with an elective cesarean delivery without labor. Because antepartum counseling cannot account for whether a woman will develop an indication requiring a repeat cesarean delivery or whether labor will occur before scheduled cesarean delivery, the purpose of this analysis was to provide clinically useful information regarding the risks of uterine rupture and adverse perinatal outcome for women at term with a history of prior cesarean delivery. METHODS: Women with a term singleton gestation and prior cesarean delivery were studied over 4 years at 19 centers. For this analysis, outcomes from five groups were studied: trial of labor, elective repeat with no labor, elective repeat with labor (women presenting in early labor who subsequently underwent cesarean delivery), indicated repeat with labor, and indicated repeat without labor. All cases of uterine rupture were reviewed centrally to assure accuracy of diagnosis. RESULTS: A total of 39,117 women were studied. In term pregnant women with a prior cesarean delivery, the overall risk for uterine rupture was 0.32% (125 of 39,117), and the overall risk for serious adverse perinatal outcome (stillbirth, hypoxic ischemic encephalopathy, neonatal death) was 106 of 39,049 (0.27%). The uterine rupture risk for indicated repeat cesarean delivery (labor or without labor) was 7 of 6,080 (0.12%); the risk for elective (no indication) repeat cesarean delivery (labor or without labor) was 4 of 17,714 (0.02%). Indicated repeat cesarean delivery increased the risk of uterine rupture by a factor of 5 (odds ratio 5.1, 95% confidence interval 1.49-17.44). In the absence of an indication, the presence of labor also increased the risk of uterine rupture (4 of 2,721 [0.15%] compared with 0 of 14,993, P<.01). The highest rate of uterine rupture occurred in women undergoing trial of labor (0.74%, 114 of 15,323). CONCLUSION: At term, the risk of uterine rupture and adverse perinatal outcome for women with a singleton and prior cesarean delivery is low regardless of mode of delivery, occurring in 3 per 1,000 women. Maternal complications occurred in 3-8% of women within the five delivery groups.     

Effect of prior vaginal delivery or prior vaginal birth after cesarean delivery on obstetric outcomes in women undergoing trial of labor

OBJECTIVE: We sought to study the effects of prior vaginal delivery or prior vaginal birth after cesarean delivery (VBAC) on the success of a trial of labor after a cesarean delivery. METHODS: An observational study of patients who underwent a trial of labor after a single low-transverse cesarean delivery. Patients with a previous cesarean delivery and no vaginal birth were compared with patients with a single vaginal delivery before or after the previous cesarean delivery. The rates of successful VBAC, uterine rupture, and scar dehiscence were analyzed. Multivariable regression was performed to adjust for confounding variables. RESULTS: Of 2,204 patients, 1,685 (76.4%) had a previous cesarean delivery and no vaginal delivery, 198 (9.0%) had a vaginal delivery before the cesarean delivery, and 321 (14.6%) had a prior VBAC. The rate of successful trial of labor was 70.1%, 81.8%, and 93.1%, respectively (P <.001). A prior VBAC was associated with fewer third- and fourth-degree lacerations (8.5% versus 2.5% versus 3.7%, P <.001) and fewer operative vaginal deliveries (14.7% versus 5.6% versus 1.9%, P <.001) but not with uterine rupture (1.5% versus 0.5% versus 0.3%, P =.12). Patients with a prior VBAC had, in addition, a higher rate of uterine scar dehiscence (21.8%) compared with patients with a previous cesarean delivery and no vaginal delivery (5.3%; P =.001). CONCLUSION: A prior vaginal delivery and, particularly, a prior VBAC are associated with a higher rate of successful trial of labor compared with patients with no prior vaginal delivery. In addition, prior VBAC is associated with an increased rate of uterine scar dehiscence.     

Minimum oxytocin dose requirement after cesarean delivery for labor arrest

OBJECTIVE: To estimate the minimum effective intravenous dose of oxytocin required for adequate uterine contraction after cesarean delivery for labor arrest. METHODS: A randomized single-blinded study was undertaken in 30 parturients undergoing cesarean deliveries under epidural anesthesia for labor arrest despite intravenous oxytocin augmentation. Oxytocin was administered as a slow intravenous bolus immediately after delivery of the infant, according to a biased coin up-down sequential allocation scheme. After assisted spontaneous delivery of the placenta, the obstetrician, blinded to the oxytocin dose, assessed uterine contraction as either satisfactory or unsatisfactory. Additional boluses of oxytocin were administered as required, followed by a maintenance infusion. Data were interpreted and analyzed by a logistic regression model at 95% confidence intervals. RESULTS: All patients received oxytocin infusions at a mean +/- standard deviation of 9.8 +/- 6.3 hours before cesarean delivery (maximum infusion dose 10.3 +/- 8.2 mU/min). The minimum effective dose of oxytocin required to produce adequate uterine response in 90% of women (ED90) was estimated to be 2.99 IU (95% confidence interval 2.32-3.67). The estimated blood loss was 1,178 +/- 716 mL. CONCLUSION: Women requiring cesarean delivery for labor arrest after oxytocin augmentation require approximately 3 IU rapid intravenous infusion of oxytocin to achieve effective uterine contraction after delivery. This dose is 9 times more than previously reported after elective cesarean delivery in nonlaboring women at term, suggesting oxytocin receptor desensitization from exogenous oxytocin administration during labor. Therefore, alternative uterotonic agents, rather than additional oxytocin, may achieve superior uterine contraction and control of blood loss during cesarean delivery for labor arrest. LEVEL OF EVIDENCE: I.     

Uterine rupture and dehiscence associated with intravaginal misoprostol cervical ripening

OBJECTIVE: To evaluate if the prostaglandin E1 analogue misoprostol, when used as an agent for cervical ripening, is associated with uterine rupture. STUDY DESIGN: We performed a two-year retrospective chart review to determine the incidence of uterine rupture in patients with a previous cesarean delivery undergoing cervical ripening or the induction of labor. RESULTS: Uterine dehiscence occurred in 1 and uterine rupture occurred in 3 of 48 women with a prior cesarean delivery treated with 50 micrograms doses of intravaginal misoprostol for cervical ripening. Uterine rupture was found in 1 of 89 women who had an oxytocin infusion for induction of labor and none of the 24 patients who received intravaginal prostaglandin E2 placed for cervical ripening. CONCLUSION: Intravaginal misoprostol appears to be associated with an increased incidence of uterine rupture when used in patients undergoing a trial of labor after cesarean.     

Vaginal birth after cesarean section at the University of Texas.

Vaginal delivery was successful in 76% of the 242 women who underwent a trial of labor after cesarean section in a prior pregnancy. Separation of the uterine scar occurred in four women (1.7%). Women whose prior cesarean section was for breech presentation had the highest rate of successful vaginal delivery (86%). The vaginal delivery rates were similar in women who delivered infants with birth weights > or = 4,000 g (73%) and < 4,000 g (76%). The use of epidural anesthesia and oxytocin may enhance the success of vaginal delivery in women undergoing a trial of labor following an earlier cesarean section.     

Uterine rupture during induced trial of labor among women with previous cesarean delivery

OBJECTIVE: This study was undertaken to compare the rates of uterine rupture during induced trials of labor after previous cesarean delivery with the rates during a spontaneous trial of labor. STUDY DESIGN: All deliveries between 1992 and 1998 among women with previous cesarean delivery were evaluated. Rates of uterine rupture were determined for spontaneous labor and different methods of induction. RESULTS: Of 2119 trials of labor, 575 (27%) were induced. The overall rate of uterine rupture was 0.71% (15/2119). The uterine rupture rate with induced trial of labor (8/575; 1.4%) was significantly higher than with a spontaneous trial of labor (7/1544; 0.45%; P =.0004). Uterine rupture rates associated with different methods of induction were compared with the rate seen with spontaneous labor and were as follows: prostaglandin E(2) gel, 2.9% (5/172; P =.004); intracervical Foley catheter, 0.76% (1/129; P =.47); and labor induction not requiring cervical ripening, 0.74% (2/274; P =.63). The uterine rupture rate associated with inductions other than with prostaglandin E(2) was 0.74% (3/474; P =.38). The relative risk of uterine rupture with prostaglandin E(2) use versus spontaneous trial of labor was 6.41 (95% confidence interval, 2. 06-19.98). CONCLUSION: Induction of labor was associated with an increased risk of uterine rupture among women with a previous cesarean delivery, and this association was highest when prostaglandin E(2) gel was used.     

The counselling of patient with prior C-section

A trial of labor after prior cesarean delivery is associated with a greater perinatal risk than is elective repeated cesarean delivery without labor, although absolute risks are low. Information and counselling aim to estimate specific risks and to balance these risks according to individual factors. Therefore, the physician has to answer two questions: (i) which would be the probability of successful vaginal delivery? (ii) which would be the risk of uterine rupture with a trial of labor? The risk factors for failure of trial of labor are: increased maternal age, obesity, and fetal macrosomia. The risk factors for uterine rupture are: increased maternal age, postpartum fever after the previous cesarean delivery, short interdelivery interval, history of at least two previous cesarean deliveries, and a history of classical incision. Conversely, other factors are of good prognosis: a prior vaginal delivery and, particularly, a prior VBAC (Vaginal Birth After Caesarean) are associated with a higher rate of successful trial of labor compared with patients with no prior vaginal delivery; ultrasonographic measurement of the lower uterine segment thickness>3.5 mm has an excellent negative predictive value for the risk of uterine defect. Finally, the wish for additional pregnancies following a cesarean section must be considered as an argument in favour of a trial of labor after accounting for the increasing risks correlated with repeated elective cesarean deliveries.