In the absence of contraindications, a trial of labor after previous cesarean is generally endorsed,1 and several studies support this approach.2–8 In previous studies, trial-of-labor success rates ranged between 60% and 90%; the rate of repeat cesareans ranged from 10% to 40%, increasing to up to 60% in women who had had two or more cesareans.2,4–17 Even after two or more previous cesarean deliveries, the success rate remained relatively high.2,7,10,14 Nevertheless, the percentage of women opting for a trial of labor after previous cesarean varied considerably (16.3–90%).9 The problem remains the rate of nonelective repeat cesareans, particularly when the procedure has to be performed as an emergency measure because of complications during labor. Recent studies have indicated that a trial of labor may lower the incidence of minor complications (eg, wound infections) but not the number of major complications (eg, uterine rupture, septicemia, and hysterectomy), many of which occur during unsuccessful trials of labor.5 An unsuccessful trial of labor must be considered a failure because it merely adds to the expenditure and frustration for both patients and medical staff.
Numerous authors have offered criteria to help decide whether a trial of labor might be successful12,15–20; however, there are very few reliable criteria that indicate when a trial of labor will fail.19 In this study, we examined the risks of delivery after previous cesarean and tried to identify additional criteria to help decide whether a trial of labor or an elective repeat cesarean should be proposed to an individual patient.
Since 1983, the Swiss Working Group of Obstetric and Gynecologic Institutions has used questionnaires to collect joint prospective data for quality-control purposes. That database consists of 457,825 admissions with deliveries, representing approximately 40% of the deliveries in Switzerland from 1983 through 1996. After excluding twin pregnancies, we found 255,453 patients with a parity of greater than 1 (the reference number in the calculations that follow). Of the 255,453 patients, 29,046 had a previous cesarean delivery. The questionnaires were completed by the treating doctors when the patient was released from the hospital. In addition to information about the delivery, we collected various data regarding the patient’s history (risk factors such as smoking, drugs, allergies, cardiovascular diseases, and socioeconomic status). A customized program featuring a filtering function was used to evaluate the records. The method of storing and retrieving the data unfortunately did not allow multivariate analysis. For significance comparisons, we used the 2 test and calculated the confidence intervals (CIs) for the relative risk (RR).
As a first step, we compared the following groups: 1) patients with previous cesarean delivery and those without previous cesarean delivery, 2) patients who chose a trial of labor and those who did not choose a trial of labor (elective repeat cesarean), 3) patients who chose a trial of labor who needed to have induction of labor and those having a trial of labor who started spontaneous contractions, and 4) patients with a successful trial of labor and those with an unsuccessful trial of labor leading to emergency repeat cesarean. We then examined the uterine-rupture group and the perinatal-death group in more detail. Finally, we tried to assess the relevant differences between the groups and to set up new guidelines to improve decision making as to when an elective repeat cesarean should be the preferred option.