Morbidity of failed labor in patients with prior cesarean section Joanne Stone, MD, Charles J. Lockwood, MD, Gertrud S. Berkowitz, PhD, Lauren Lynch, MD, Manuel Alvarez, MD, Robert H. Lapinski, PhD, and Richard L. Berkowitz, MD New York, New York OBJECTIVE: The aim of our study was to determine whether the reported increased morbidity associated with failed attempted vaginal birth after cesarean section is attributable to the presence of a uterine scar alone or to labor preceding a cesarean section. STUDY DESIGN: Primiparous women (N = 237) who underwent repeat cesarean section after a failed trial of vaginal birth after cesarean section were retrospectively compared with 1582 nulliparous women who underwent a primary cesarean section after a failed trial of labor. RESULTS: There were no significant differences in maternal or neonatal morbidity between the two groups except for an increase in the prevalence of thin meconium in patients undergoing primary cesarean section. CONCLUSION: Our results suggest that the presence of a previous cesarean section scar does not increase the overall baseline morbidity associated with cesarean section after labor. (AM J OBSTET GYNECOL 1992;167:1513-7.)
Key words: Vaginal birth after cesarean section, morbidity, failed labor The obstetric literature has proved that vaginal birth after cesarean section is safe and efficacious in appropriately selected patients and hospital settings. I -6 Success rates for vaginal birth after cesarean section have ranged from 61 % to 80% in large clinical studies. Morbidity and mortality in women undergoing a successful trial of labor after cesarean section have been shown to be equivalent to or lower than morbidity and mortality in women undergoing elective repeat cesarean section. 6 -" In fact, in a review of the Englishlanguage literature between 1950 and 1980, Lavin et aJ.9 could find no cases of maternal death caused by uterine rupture during labor. Numerous studies, however, have documented a significantly increased morbidity in women undergoing repeat cesarean section after a failed attempt of vaginal birth after cesarean section. 6 - 8 • 10-16 Higher rates of febrile morbidity, uterine scar dehiscence or rupture, endometritis, transfusion, and wound infection have been noted in these patients. The majority of these studies, however, have compared women undergoing repeat cesarean section after a failed attempt at vaginal From the Department of Obstetrics, Gynecology, and Reproductive Science, Mount Sinai Medical Center. Presented in part at the Thirty-ninth Annual Meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 18-21, 1992.
Reprint requests: Joanne Stone, MD, Department of Obstetrics, Gynecology, and Reproductive Science, Mount Sinai Medical Center, One Gustave L. Levy Pl., Box 1171, New York, NY 10029 6/6/41901
birth after cesarean section with women undergoing both a successful vaginal birth after cesarean section and an elective repeat cesarean section. A crucial question that has not been directly addressed in these studies is whether the increased morbidity associated with failed vaginal birth after cesarean section is attributable to the presence of a uterine scar alone or to labor preceding a cesarean section. To answer this question we compared maternal and neonatal morbidity in primiparous patients undergoing repeat cesarean section after a failed trial of labor with nulliparous women undergoing primary cesarean section after labor. A nulliparous control group was selected because there is evidence indicating that the course of labor in primiparous women with a previous cesarean section most closely approximates that of nulliparous parturients. 17
Material and methods A computerized perinatal database was used to retrospectively identify 1819 patients who were delivered at the Mount Sinai Hospital in New York City between the years 1987 to 1990 and who fulfilled the inclusion criteria for the study. The failed vaginal birth after cesarean section group consisted of 237 primiparous patients with singleton gestations and a history of one previous cesarean section who underwent repeat cesarean section after an unsuccessful trial of labor. The primary cesarean section group consisted of 1582 nulliparous women with singleton gestations who under1513
1514
Stone et al.
Table I. Indications for cesarean section rank-ordered from most important to least important Fetal distress Cord prolapse Failed forceps Abruptio placentae Cephalopelvic disproportion-failure to progress Amnionitis Abnormal presentation-position Other
went a primary cesarean section after labor during the same time interval. Patients who had an elective repeat cesarean section were not included in the study. All labor and deliveries were managed by residents and attending obstetricians at the Mount Sinai Hospital. Women with a previous classic or T incision were excluded from a trial of labor, and women with a low vertical incision (n = 5) or unknown scar (n = 82) were allowed a trial of labor. During labor, fetal heart rate and uterine activity were electronically monitored in both groups of patients. Oxytocin and epidural anesthesia were used with the same obstetric indications and contraindications in both groups. The information used in this analysis was retrieved from the computerized database that comprises detailed information on the prenatal, intrapartum, and postpartum course and on neonatal outcome. Details of this database have been described elsewhere. IS The groups were compared for differences in maternal demographic factors, labor and delivery characteristics, indications for cesarean section, postpartum complications, and maternal and neonatal morbidity and mortality. A comparison of the indications for cesarean section between the two groups was performed. If more than one indication was present, the indication was rankordered on a scale from the most important to the least important, and the most important indication was assigned to that patient. For example, if amnionitis and fetal distress were listed as indications for cesarean section, fetal distress was ranked higher and thus considered the primary indication. The same scale was used in both groups of patients and is presented in Table I. The charts of all patients in which the terms "uterine rupture" or "uterine dehiscence" were identified were reviewed. For our study uterine rupture was defined as any defect associated with excessive maternal pain and vaginal bleeding or a fetal heart tracing demonstrating severe variable decelerations, late decelerations, or prolonged bradycardia. Uterine scar dehiscence was defined as a small defect in the integrity of the uterine scar discovered incidentally at the time of repeat cesarean section.
December 1992 Am J Obstet Gynecol
A X2 test or, in the case of small cell sizes, a Fisher exact test was used to analyze categoric data. In analyzing the duration of labor and the duration of ruptured membranes, a log transformation of the data was performed to normalize the distribution, after which a Student t test was performed. A p value < 0.05 was considered statistically significant. Logistic regression was then performed to control for possible confounding factors. Our study had sufficient power to detect a difference of 6% to 7% for all variables with an alpha = 0.05 and power = 0.80. Results
Table II shows the maternal characteristics for the failed vaginal birth after cesarean section group and the primary cesarean section group. There was a significantly higher frequency of private patients, women aged < 20, white patients, and patients with diabetes in the primary cesarean section group compared with the failed vaginal birth after cesarean section group. The failed vaginal birth after cesarean section group had a higher frequency of preterm births and Hispanic women. There were no significant differences in the proportion of black women or the frequency of preeclampsia or chronic hypertension. Table III shows a comparison of the intrapartum characteristics between both groups. The nulliparous patients undergoing primary cesarean section had a significantly higher frequency of oxytocin use, thin meconium, and amnionitis than the failed vaginal birth after cesarean section group. The nulliparous group also had a significantly longer mean duration of labor (12.6 ± 7.1 hr vs 10.4 ± 6.3 hr, p < 0.001) and a longer mean duration of ruptured membranes (10.9 ± 8.9 hrvs 7.3 ± 7.2 hr, p < 0.001) than the patients with failed vaginal birth after cesarean sections. There were no significant differences in fetal presentation, epidural use, thick meconium, antibiotic use, or excessive blood loss at cesarean section. Our database could not distinguish between epidural anesthesia administered for analgesia during labor and epidural anesthesia administered in preparation for cesarean section. The indications for cesarean section are presented in Table IV. There were no significant differences between the two groups. Cesarean section performed for cephalopelvic disproportion-failure to progress was the most common indication, followed by fetal distress and abnormal presentation-position. When each indication was taken into account and assessed separately, similar results were also obtained. A comparison of maternal morbidity and mortality demonstrated no significant differences between the groups. The parameters examined included hospitalization > 6 days (10.2% for the failed vaginal birth after cesarean section group vs 11.4% for the primary cesarean section group), lacerations or uterine extensions
Morbidity of repeat cesarean section after labor
Volume 167 l':umber 6
1515
Table II. Maternal characteristics
r
Characteristics
Failed vaginal birth after cesarean section (%)
cesarean section (%)
p Value
Age
Key words: Vaginal birth after cesarean section, morbidity, failed labor The obstetric literature has proved that vaginal birth after cesarean section is safe and efficacious in appropriately selected patients and hospital settings. I -6 Success rates for vaginal birth after cesarean section have ranged from 61 % to 80% in large clinical studies. Morbidity and mortality in women undergoing a successful trial of labor after cesarean section have been shown to be equivalent to or lower than morbidity and mortality in women undergoing elective repeat cesarean section. 6 -" In fact, in a review of the Englishlanguage literature between 1950 and 1980, Lavin et aJ.9 could find no cases of maternal death caused by uterine rupture during labor. Numerous studies, however, have documented a significantly increased morbidity in women undergoing repeat cesarean section after a failed attempt of vaginal birth after cesarean section. 6 - 8 • 10-16 Higher rates of febrile morbidity, uterine scar dehiscence or rupture, endometritis, transfusion, and wound infection have been noted in these patients. The majority of these studies, however, have compared women undergoing repeat cesarean section after a failed attempt at vaginal From the Department of Obstetrics, Gynecology, and Reproductive Science, Mount Sinai Medical Center. Presented in part at the Thirty-ninth Annual Meeting of the Society for Gynecologic Investigation, San Antonio, Texas, March 18-21, 1992.
Reprint requests: Joanne Stone, MD, Department of Obstetrics, Gynecology, and Reproductive Science, Mount Sinai Medical Center, One Gustave L. Levy Pl., Box 1171, New York, NY 10029 6/6/41901
birth after cesarean section with women undergoing both a successful vaginal birth after cesarean section and an elective repeat cesarean section. A crucial question that has not been directly addressed in these studies is whether the increased morbidity associated with failed vaginal birth after cesarean section is attributable to the presence of a uterine scar alone or to labor preceding a cesarean section. To answer this question we compared maternal and neonatal morbidity in primiparous patients undergoing repeat cesarean section after a failed trial of labor with nulliparous women undergoing primary cesarean section after labor. A nulliparous control group was selected because there is evidence indicating that the course of labor in primiparous women with a previous cesarean section most closely approximates that of nulliparous parturients. 17
Material and methods A computerized perinatal database was used to retrospectively identify 1819 patients who were delivered at the Mount Sinai Hospital in New York City between the years 1987 to 1990 and who fulfilled the inclusion criteria for the study. The failed vaginal birth after cesarean section group consisted of 237 primiparous patients with singleton gestations and a history of one previous cesarean section who underwent repeat cesarean section after an unsuccessful trial of labor. The primary cesarean section group consisted of 1582 nulliparous women with singleton gestations who under1513
1514
Stone et al.
Table I. Indications for cesarean section rank-ordered from most important to least important Fetal distress Cord prolapse Failed forceps Abruptio placentae Cephalopelvic disproportion-failure to progress Amnionitis Abnormal presentation-position Other
went a primary cesarean section after labor during the same time interval. Patients who had an elective repeat cesarean section were not included in the study. All labor and deliveries were managed by residents and attending obstetricians at the Mount Sinai Hospital. Women with a previous classic or T incision were excluded from a trial of labor, and women with a low vertical incision (n = 5) or unknown scar (n = 82) were allowed a trial of labor. During labor, fetal heart rate and uterine activity were electronically monitored in both groups of patients. Oxytocin and epidural anesthesia were used with the same obstetric indications and contraindications in both groups. The information used in this analysis was retrieved from the computerized database that comprises detailed information on the prenatal, intrapartum, and postpartum course and on neonatal outcome. Details of this database have been described elsewhere. IS The groups were compared for differences in maternal demographic factors, labor and delivery characteristics, indications for cesarean section, postpartum complications, and maternal and neonatal morbidity and mortality. A comparison of the indications for cesarean section between the two groups was performed. If more than one indication was present, the indication was rankordered on a scale from the most important to the least important, and the most important indication was assigned to that patient. For example, if amnionitis and fetal distress were listed as indications for cesarean section, fetal distress was ranked higher and thus considered the primary indication. The same scale was used in both groups of patients and is presented in Table I. The charts of all patients in which the terms "uterine rupture" or "uterine dehiscence" were identified were reviewed. For our study uterine rupture was defined as any defect associated with excessive maternal pain and vaginal bleeding or a fetal heart tracing demonstrating severe variable decelerations, late decelerations, or prolonged bradycardia. Uterine scar dehiscence was defined as a small defect in the integrity of the uterine scar discovered incidentally at the time of repeat cesarean section.
December 1992 Am J Obstet Gynecol
A X2 test or, in the case of small cell sizes, a Fisher exact test was used to analyze categoric data. In analyzing the duration of labor and the duration of ruptured membranes, a log transformation of the data was performed to normalize the distribution, after which a Student t test was performed. A p value < 0.05 was considered statistically significant. Logistic regression was then performed to control for possible confounding factors. Our study had sufficient power to detect a difference of 6% to 7% for all variables with an alpha = 0.05 and power = 0.80. Results
Table II shows the maternal characteristics for the failed vaginal birth after cesarean section group and the primary cesarean section group. There was a significantly higher frequency of private patients, women aged < 20, white patients, and patients with diabetes in the primary cesarean section group compared with the failed vaginal birth after cesarean section group. The failed vaginal birth after cesarean section group had a higher frequency of preterm births and Hispanic women. There were no significant differences in the proportion of black women or the frequency of preeclampsia or chronic hypertension. Table III shows a comparison of the intrapartum characteristics between both groups. The nulliparous patients undergoing primary cesarean section had a significantly higher frequency of oxytocin use, thin meconium, and amnionitis than the failed vaginal birth after cesarean section group. The nulliparous group also had a significantly longer mean duration of labor (12.6 ± 7.1 hr vs 10.4 ± 6.3 hr, p < 0.001) and a longer mean duration of ruptured membranes (10.9 ± 8.9 hrvs 7.3 ± 7.2 hr, p < 0.001) than the patients with failed vaginal birth after cesarean sections. There were no significant differences in fetal presentation, epidural use, thick meconium, antibiotic use, or excessive blood loss at cesarean section. Our database could not distinguish between epidural anesthesia administered for analgesia during labor and epidural anesthesia administered in preparation for cesarean section. The indications for cesarean section are presented in Table IV. There were no significant differences between the two groups. Cesarean section performed for cephalopelvic disproportion-failure to progress was the most common indication, followed by fetal distress and abnormal presentation-position. When each indication was taken into account and assessed separately, similar results were also obtained. A comparison of maternal morbidity and mortality demonstrated no significant differences between the groups. The parameters examined included hospitalization > 6 days (10.2% for the failed vaginal birth after cesarean section group vs 11.4% for the primary cesarean section group), lacerations or uterine extensions
Morbidity of repeat cesarean section after labor
Volume 167 l':umber 6
1515
Table II. Maternal characteristics
r
Characteristics
Failed vaginal birth after cesarean section (%)
cesarean section (%)
p Value
Age
