在既往有剖宫产史的妇女中进行引产
Obstetrics
Misoprostol induction of labor among women with a history of cesarean delivery ☆
Presented at the Twentieth Annual Meeting of the Society for Maternal-Fetal Medicine, Miami Beach, Florida, January 31–February 5, 2000.
Leslie Choy-Hee, MD, B.Denise Raynor, MD
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DOI: 10.1067/mob.2001.115177
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Abstract
Objective: Several reports have appeared of uterine rupture among women with a history of cesarean delivery who received misoprostol for induction of labor. A recent review suggested a uterine rupture rate of almost 6%, but the experience at our institution did not seem to reflect this high complication rate. This study was undertaken to compare complications of labor induction with misoprostol between women with a history of cesarean delivery and women without uterine scarring. Study Design: A computerized database was used to select women with a viable fetus who underwent induction of labor with misoprostol during the period from January 1996 through December 1998. Patients were given 50 μg misoprostol every 4 hours. Women with a history of cesarean delivery were retrospectively compared with those without uterine scarring. Results: A total of 425 women were given misoprostol for induction of labor: 48 had a history of cesarean delivery and 377 did not. Women with a history of cesarean delivery were more likely to be delivered abdominally (56% vs 28%; P < .04). Among women with a history of cesarean delivery, women who had a history of vaginal birth after cesarean were more likely to be delivered vaginally (92% vs 42%; P = .003). There was no difference in the overall rate of complications (2% with scarring vs 3% without scarring). There were no uterine ruptures. However, the previous cesarean group was more likely than the unscarred group to have blood loss >500 mL (38% vs 22%; P < .03). Although the incidences of fetal distress were similar, neonates born to women in the previous cesarean group were more likely to have an Apgar score <7 at 5 minutes (13% vs 5%; P < .04). Conclusion: Misoprostol induction of labor in women with a history of cesarean resulted in a higher rate of cesarean delivery than was seen among women without uterine scarring but was not associated with a higher incidence of complications. There were no uterine ruptures in either group. (Am J Obstet Gynecol 2001;184:1115-7.)
Keywords
Labor induction; misoprostol; previous cesarean delivery
Labor induction continues to be a common aspect of obstetric practice, with 15% of all pregnant women undergoing induction or augmentation. Cervical ripening shortens the length of induction.1 Vaginal application of prostaglandin E2, including suppositories and dinoprostone gel and inserts, has been extensively used and studied.1 Because of the high cost and the need for refrigerated storage, many practitioners have turned to the prostaglandin E1 analog misoprostol. However, misoprostol has demonstrated consistently higher rates of uterine tachysystole.2 More alarming is the growing number of reports, both published and anecdotal, of uterine rupture in women with a history of cesarean delivery who receive misoprostol.3, 4, 5 and 6 Misoprostol has been used extensively at our institution for induction of labor in women with and without uterine scarring. We performed a retrospective review to evaluate the safety and efficacy of misoprostol use among women with a history of cesarean delivery and to compare them with those among women without uterine scarring.
Material and methods
A computerized perinatal database was used to select patients who had misoprostol administered intravaginally for induction of labor between January 1996 and December 1998 at Grady Memorial Hospital, Atlanta. Data extracted included parity, induction indications, number and types of uterine scars, indication for primary cesarean delivery, labor complications, birth weight, Apgar score at 5 minutes, use of epidural analgesia, and route of delivery. Criteria for patients receiving misoprostol included singleton gestation, Bishop score <6, cephalic presentation, and reassuring fetal heart rate pattern. A 50-μg dose of misoprostol was placed in the posterior vaginal fornix at 4-hour intervals for as long as 24 hours. Misoprostol use was discontinued with cervical dilatation of 2 cm or a regular contraction pattern or with rupture of membranes and regular contractions. Oxytocin augmentation was used when labor failed to progress or 4 hours after the maximum of 6 doses of misoprostol had failed to achieve active labor.
Groups were compared with respect to labor complications, mode of delivery, Apgar scores at 5 minutes, and use of epidural anesthesia. Statistical analysis was performed with the χ2 test, with the Fisher exact test when appropriate. P < .05 was considered statistically significant. This study was approved by the institutional human investigations committee of Emory University.
Results
A total of 425 women were included in the analysis:48 women had a history of at least one previous cesarean delivery, and the remaining 377 women had no history of uterine surgery. Women with a history of cesareandelivery were more likely to be delivered abdominally than were women without uterine scarring (56% vs 28%; P < .04).
There was no difference between the overall rates of complications (2% with scarring vs 3% without scarring). Complications included abruptio placentae, retained placenta, uterine atony, and blood transfusion. There were no uterine dehiscences or ruptures. However, women with a history of cesarean delivery were more likely to have blood loss >500 mL than were those without uterine scarring (38% vs 22%; P < .03). The incidences of fetal distress in the two groups were similar (23% with scarring vs 20% without scarring). However, neonates born to women with a history of cesarean delivery were more likely to have an Apgar score <7 at 5 minutes than were those born to women without uterine scarring (13% vs 5%; P < .04).
The rates of oxytocin augmentation were similar (44% with scarring vs 45% without scarring). Epidural anesthesia for labor was more common in the previous cesarean group (58% vs 39%; P < .02).
Among the 48 women with a history of cesarean delivery, 35 (73%) had a documented low transverse incision and 13 (27%) had unknown incisions. Six of the 48 had undergone two previous cesarean deliveries; the remaining had undergone only one. Twenty-eight of the women (58%) had only one previous delivery; the remaining 20 had two to five previous deliveries, and 12 of these had undergone at least one vaginal birth after cesarean. Indications for primary cesarean deliveries included arrest disorders in 22 cases (46%), breech presentation in 8 cases (17%), nonreassuring fetal heart tracing in 8 cases (17%), and other indications in 8 cases (17%).
Among the women with a history of cesarean delivery, those with a previous vaginal birth after cesarean were more likely to be delivered vaginally (92% vs 42%; P = .003), as were women who had more than one previous delivery (75% vs 42%; P = .014). There was no difference in the proportion of vaginal deliveries between women with documented low transverse scars and those with undocumented scars. Among those for whom the indication for primary cesarean delivery was an arrest disorder, 36% were delivered vaginally, and 50% of those delivered abdominally had the same indication as in the previous cesarean delivery. Among those with a nonrecurring indication for the primary cesarean delivery, such as breech or a nonreassuring fetal heart tracing, 58% were delivered vaginally. This difference was not significant.
Comment
This investigation found few differences in complications associated with the vaginal administration of misoprostol for labor induction between women with a history of cesarean delivery and those without uterine scarring. The finding that fewer women with a history of cesarean delivery were delivered vaginally is not surprising, because success rates for trial of labor range from 40% to 80% and may be lower in the setting of induction.7 More women in the group with uterine scarring had blood loss >500 mL, which probably reflects that group’s higher cesarean delivery rate. This additional blood loss, however, did not result in a higher rate of blood transfusion. The higher use of epidural anesthesia for labor in the previous cesarean group may be related to previous experience with labor and epidural anesthesia. It may also reflect physician bias, which encouraged patients to receive epidural anesthesia in anticipation of the higher probability of abdominal delivery among women with a history of cesarean delivery.
The higher incidence of an Apgar score <7 at 5 minutes among women with a history of cesarean delivery appears to be of somewhat more concern, although the incidences of fetal distress in the two groups were similar. Although the diagnosis of fetal distress reflects fetal heart rate monitoring, rather than neonatal status, neither fetal heart tracing nor Apgar score at 5 minutes is a good predictor of long-term infant morbidity. Lower Apgar scores may reflect differences in the proportions of and indications for cesarean delivery. Data on neonatal outcome were not analyzed.
Among women with a history of cesarean delivery who had labor induction with misoprostol, factors associated with successful vaginal delivery were similar to those usually associated with successful trial of labor: previous vaginal delivery and previous vaginal birth after cesarean. Although the rate of vaginal delivery was higher among women with nonrecurring indications for primary cesarean delivery, this difference was not statistically significant.
No uterine ruptures or dehiscences occurred among the 48 women with a history of cesarean delivery. Although these data appear reassuring, the power of this study is limited by the sample size. This contrast with reports in the literature highlights the difficulty in interpreting isolated case reports and small clinical trials. Plaut et al3 calculated a rupture rate of 5.6% in a review of the experience at a single hospital. Combination of these cases with other reports would yield a 4.7% rupture rate.4 and 5 Although several of these patients had additional confounding risk factors for uterine rupture, the absence of dehiscence in our sample is within the 95th percentile for a rupture rate at this level.
Should misoprostol be used to induce labor among women with a history of cesarean delivery? This question may be difficult to answer. One trial has already been terminated, and women with attempted vaginal birth after cesarean were excluded from another trial after a uterine rupture, both because of concern for patient safety.4 and 6 Recently The American College of Obstetricians and Gynecologists has recommended the discontinuation of misoprostol use among women with a history of cesarean delivery.8 A number of questions remain to be answered. Are there other factors that place patients at risk for uterine rupture? These could include the number of previous cesarean deliveries, the type of incision, the misoprostol dosing regimen, and the duration of oxytocin augmentation. Perhaps the best approach would be a multicenter retrospective study comparing misoprostol with other cervical ripening and induction agents and with spontaneous labor among women attempting vaginal birth after cesarean.
