A randomized trial of misoprostol and extra-amniotic saline infusion for cervical ripening and labor induction

Mechanical methods for induction of labour

BACKGROUND

Mechanical methods were the first methods developed to ripen the cervix and induce labour. During recent decades they have been substituted by pharmacological methods. Potential advantages of mechanical methods, compared with pharmacological methods may include reduction in side effects that could improve neonatal outcomes. This is an update of a review first published in 2001, last updated in 2012.

OBJECTIVES

To determine the effectiveness and safety of mechanical methods for third trimester (> 24 weeks' gestation) induction of labour in comparison with prostaglandin E2 (PGE2) (vaginal and intracervical), low-dose misoprostol (oral and vaginal), amniotomy or oxytocin.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies (9 January 2018). We updated the search in March 2019 and added the search results to the awaiting classification section of the review.

SELECTION CRITERIA

Clinical trials comparing mechanical methods used for third trimester cervical ripening or labour induction with pharmacological methods.Mechanical methods include: (1) the introduction of a catheter through the cervix into the extra-amniotic space with balloon insufflation; (2) introduction of laminaria tents, or their synthetic equivalent (Dilapan), into the cervical canal; (3) use of a catheter to inject fluid into the extra-amniotic space (EASI).This review includes the following comparisons: (1) specific mechanical methods (balloon catheter, laminaria tents or EASI) compared with prostaglandins (different types, different routes) or with oxytocin; (2) single balloon compared to a double balloon; (3) addition of prostaglandins or oxytocin to mechanical methods compared with prostaglandins or oxytocin alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and assessed risk of bias. Two review authors independently extracted data and assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

This review update includes a total of 113 trials (22,373 women) contributing data to 21 comparisons. Risk of bias of trials varied. Overall, the evidence was graded from very-low to moderate quality. All evidence was downgraded for lack of blinding and, for many comparisons, the effect estimates were too imprecise to make a valid judgement.Balloon versus vaginal PGE2: there may be little or no difference in vaginal deliveries not achieved within 24 hours (average risk ratio (RR) 1.01, 95% confidence interval (CI) 0.82 to 1.26; 7 studies; 1685 women; I² = 79%; low-quality evidence) and there probably is little or no difference in caesarean sections (RR 1.00, 95% CI 0.92 to 1.09; 28 studies; 6619 women; moderate-quality evidence) between induction of labour with a balloon catheter and vaginal PGE2. A balloon catheter probably reduces the risk of uterine hyperstimulation with fetal heart rate (FHR) changes (RR 0.35, 95% CI 0.18 to 0.67; 6 studies; 1966 women; moderate-quality evidence), serious neonatal morbidity or perinatal death (RR 0.48, 95% CI 0.25 to 0.93; 8 studies; 2757 women; moderate-quality evidence) and may slightly reduce the risk of aneonatal intensive care unit (NICU) admission (RR 0.82, 95% CI 0.65 to 1.04; 3647 women; 12 studies; low-quality evidence). It is uncertain whether there is a difference in serious maternal morbidity or death (RR 0.20, 95% CI 0.01 to 4.12; 4 studies; 1481 women) or five-minute Apgar score < 7 (RR 0.74, 95% CI 0.49 to 1.14; 4271 women; 14 studies) because the quality of the evidence was found to be very low and low, respectively.Balloon versus low-dose vaginal misoprostol: it is uncertain whether there is a difference in vaginal deliveries not achieved within 24 hours between induction of labour with a balloon catheter and vaginal misoprostol (RR 1.09, 95% CI 0.85 to 1.39; 340 women; 2 studies; low-quality evidence). A balloon catheter probably reduces the risk of uterine hyperstimulation with FHR changes (RR 0.39, 95% CI 0.18 to 0.85; 1322 women; 8 studies; moderate-quality evidence) but may increase the risk of a caesarean section (average RR 1.28, 95% CI 1.02 to 1.60; 1756 women; 12 studies; I² = 45%; low-quality evidence). It is uncertain whether there is a difference in serious neonatal morbidity or perinatal death (RR 0.58, 95% CI 0.12 to 2.66; 381 women; 3 studies), serious maternal morbidity or death (no events; 4 studies, 464 women), both very low-quality evidence, and five-minute Apgar score < 7 (RR 1.00, 95% CI 0.50 to 1.97; 941 women; 7 studies) and NICU admissions (RR 1.00, 95% CI 0.61 to 1.63; 1302 women; 9 studies) both low-quality evidence.Balloon versus low-dose oral misoprostol: a balloon catheter probably increases the risk of a vaginal delivery not achieved within 24 hours (RR 1.28, 95% CI 1.13 to 1.46; 782 women, 2 studies, and probably slightly increases the risk of a caesarean section (RR 1.17, 95% CI 1.04 to 1.32; 3178 women; 7 studies; both moderate-quality evidence) when compared to oral misoprostol. It is uncertain whether there is a difference in uterine hyperstimulation with FHR changes (RR 0.81, 95% CI 0.48 to 1.38; 2033 women; 2 studies), serious neonatal morbidity or perinatal death (RR 1.11, 95% CI 0.60 to 2.06; 2627 women; 3 studies), both low-quality evidence, serious maternal morbidity or death (RR 0.50, 95% CI 0.05 to 5.52; 2627 women; 3 studies), very low-quality evidence, five-minute Apgar scores < 7 (RR 0.71, 95% CI 0.38 to 1.32; 2693 women; 4 studies) and NICU admissions (RR 0.82, 95% CI 0.58 to 1.17; 2873 women; 5 studies) both low-quality evidence.

AUTHORS' CONCLUSIONS

Low- to moderate-quality evidence shows mechanical induction with a balloon is probably as effective as induction of labour with vaginal PGE2. However, a balloon seems to have a more favourable safety profile. More research on this comparison does not seem warranted.Moderate-quality evidence shows a balloon catheter may be slightly less effective as oral misoprostol, but it remains unclear if there is a difference in safety outcomes for the neonate. When compared to low-dose vaginal misoprostol, low-quality evidence shows a balloon may be less effective, but probably has a better safety profile.Future research could be focused more on safety aspects for the neonate and maternal satisfaction.

Misoprostol for Labour Induction after Previous Caesarean Section - Forever a "No Go"?

Misoprostol in oral or vaginal form is an established method of labour induction worldwide. Its use after previous caesarean section is associated with a high rate of uterine rupture; according to international guidelines it is therefore contraindicated in this setting. However the evidence base for this recommendation comprises case reports, one randomised trial that was discontinued prematurely, and numerous low quality retrospective data analyses published between 1997 and 2004. New insights into e.g. resorption kinetics, dosage and application intervals, dose dependant uterine hyperstimulation rates, as well as increasing clinical experience with misoprostol have lead to a critical reappraisal of these "historical" studies. Accordingly the evidence supporting a ban on vaginal and particularly oral misoprostol for labour induction in the context of a scarred uterus is currently insufficient for a convincing guideline recommendation. In view of the clear advantages of misoprostol over prostaglandin E₂ (cheaper, more effective) a retrospective review of registry data should be conducted to determine the incidence of uterine rupture following misoprostol and the circumstances in which it occurs. A prospective, randomised trial could then be conducted on the basis of these findings (e.g. oral misoprostol vs. vaginal prostaglandin E₂); known risk factors for uterine rupture including the type of uterine scar would need to be taken into account when selecting patients for vaginal delivery. Until new data from well-designed studies are available, misoprostol will continue to be contraindicated in clinical guidelines for use in labour induction after previous caesarean section.

A critical appraisal of the misoprostol removable, controlled-release vaginal delivery system of labor induction

BACKGROUND

Induction of labor is a major issue in pregnancy management. Finding strategies to increase rate and decrease time to vaginal delivery is an important goal, but maternal or neonatal safety must remain the primary objective. Misoprostol is a synthetic analogue of prostaglandin used off label to ripen the cervix and induce labor. The misoprostol vaginal insert (MVI) was designed to allow a controlled-release delivery of misoprostol (from 50 to 200 μg) with a removal tape. The objective of this review was to make a critical appraisal of this device referring to the literature.

METHODS

A literature search was performed in the PubMed and Cochrane databases using the keywords "vaginal misoprostol insert".

RESULTS

Several studies compared different doses of MVI (50, 100, 150, and 200 μg) with the 10 mg dinoprostone insert. The 100 μg MVI compared with the dinoprostone vaginal insert (DVI) showed similar efficacy and no significant differences in cesarean delivery rate. MVI 200 μg compared with DVI showed a reduced time to vaginal delivery and oxytocin need but had an increased risk of uterine hyperstimulation. The rate of hyperstimulation syndrome was two to three times more frequent with the 200 μg MVI than the 100 μg.

CONCLUSION

Current data suggest that the 100 μg MVI would provide the best balance between efficacy and safety. Further studies should be performed to evaluate this dose, especially in high-risk situations needing induction of labor.

The effect of a Foley catheter balloon on cervical ripening

The Foley catheter balloon may affect cervical ripening through changes in biochemical mediators by immunoassay and immunohistochemistry, when it is used for pre-induction cervical ripening. The aim of the study was to evaluate the changes in the biochemical mediators from the extra-amniotic space and immunohistochemistry in ripened cervical tissue after the insertion of a Foley catheter balloon (FCB) for pre-induction cervical ripening. A total of 18 pregnant women with a Bishop's score < 6, who were undergoing labour induction, were evaluated in this prospective study. The FCB was irrigated with 10 ml of phosphate buffered saline and the irrigant was collected 0, 2, 4 and 8 h after placement of the FCB or until spontaneous expulsion of the FCB occurred. Irrigant specimens were also collected from 10 spontaneous labouring (SL) women in the active phase of labour. The levels of interleukin (IL)-6, IL-8, matrix metalloproteinase (MMP)-8 and NO were measured. Cervical specimens were obtained from 12 women, including four undergoing induction; four SL and four non-pregnant (NP) women. Immunohistochemical staining was performed to localise hyaluronic acid synthase (HAS)-1, IL-6, IL-8, MMP-8, endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS). Results showed that the levels of IL-6, IL-8, and MMP-8 significantly increased over time in FCB group (p < 0.01). In the immunohistochemical analysis of cervical tissues, immunoreactivity of HAS-1 in the after FCB group was stronger than any of the other groups. The protein expressions of IL-6, IL-8, MMP-8, eNOS and iNOS were more prominent in the after FCB and SL groups than in the NP and the before FCB groups. iNOS was only observed in the after FCB and SL groups. It was concluded that FCB may affect cervical ripening through changes in biochemical mediators by immunoassay and immunohistochemistry, when it is used for pre-induction cervical ripening.

Foley catheter balloon vs locally applied prostaglandins for cervical ripening and labor induction: a systematic review and metaanalysis

We performed a metaanalysis of publications comparing the efficacy and safety of cervical ripening and labor induction by Foley catheter balloon (FCB) vs locally applied prostaglandins (LAPG) in the third trimester of pregnancy. Twenty-seven randomized controlled trials (1966-2008; 3532 participants) were selected from MEDLINE, EMBASE, and CENTRAL searches. There was no significant difference between FCB and LAPG in cesarean delivery rates. LAPG had a significantly increased risk of excessive uterine activity (P = .001). FCB had a significantly higher risk of oxytocin induction/augmentation during labor (P = .0002). Cervical prostaglandin-E2 was less effective (P = .04), and vaginal prostaglandin-E1 bore a significantly higher risk of excessive uterine activity (P < .0001) and meconium staining (P = .04). We concluded that FCB and LAPG result in similar cesarean delivery rates, that FCB bears a higher risk of oxytocin use for labor induction and/or augmentation, and that LAPG carries a higher risk of contraction abnormalities.

Do mechanical methods of cervical ripening increase infectious morbidity? A systematic review

The purpose of this study was to review systematically randomized controlled trials that were associated with cervical ripening. We identified randomized controlled trials that compared the use of Foley catheter, with or without extraamniotic saline solution infusion, Laminaria, or hygroscopic dilators for cervical ripening or induction with pharmacologic agents or placebo. Randomized controlled trials that evaluated maternal or neonatal infection were selected. The outcomes that were assessed were maternal and neonatal infection, chorioamnionitis, and endomyometritis. Thirty studies met inclusion criteria. Compared with the use of pharmacologic methods alone, patients who underwent cervical ripening with mechanical agents had a significantly higher rate of maternal infection rates. Similar results were noted for patients who underwent ripening with Foley catheter alone in comparison with pharmacologic agents. No difference was noted in maternal infection rates for patients who underwent ripening with extraamniotic saline solution infusion, Laminaria, or hygroscopic dilators. Compared with the use of pharmacologic agents alone, maternal and neonatal infectious morbidity appears to be increased when mechanical agents are used for cervical ripening.

Induction of labor using a foley balloon, with and without extra-amniotic saline infusion

OBJECTIVE

To compare transcervical Foley bulb with and without extra-amniotic saline infusion for induction of labor in patients with an unfavorable cervix.

METHODS

Women who presented for induction of labor with Bishop score less than 5 were randomly assigned to receive Foley alone or Foley with extra-amniotic saline infusion for induction of labor. Primary outcome was time from start of induction to vaginal delivery. Secondary outcomes were cesarean delivery rates, incidence of chorioamnionitis, Apgar scores at 1 and 5 minutes, and adverse events.

RESULTS

One hundred forty women completed the study. Time from induction to vaginal delivery was 16.58 (+/- 7.55) hours in the extra-amniotic saline infusion group compared with 21.47 (+/- 9.95) hours in the Foley group (P < .01). Chorioamnionitis occurred in 4 of 66 (6.1%) women in the extra-amniotic saline infusion group compared with 12 of 74 (16.2%) women in the Foley group (P = .067). Cesarean delivery rate was 21.2% versus 20.1% in the extra-amniotic saline infusion and Foley groups, respectively (P = 1.0). Median 1-minute and 5-minute Apgar scores were 9 in both groups. Adverse events were rare and unrelated to method of induction.

CONCLUSION

Induction of labor by using Foley with extra-amniotic saline infusion results in shorter induction-to-vaginal-delivery time than Foley alone, without affecting cesarean delivery rates.

LEVEL OF EVIDENCE

II-I

Randomised trial of intravaginal misoprostol and intracervical Foley catheter for cervical ripening and induction of labour

Induction of labour may be indicated despite an unripe cervix. The purpose of this study was to compare the safety and efficacy of intravaginal misoprostol and an intracervical Foley's balloon catheter for preinduction cervical ripening and labour induction. A total of 120 patients requiring indicated induction of labour with an unfavourable cervix (Bishop's score < or =4) were randomised prospectively to receive either 50 mug intravaginal misoprostol every 6 h for a maximum of two doses, or an intracervical Foley balloon catheter for 12 h followed by an intravenous oxytocin infusion. The two arms of the study were comparable with respect to maternal age, parity, gestational age, indication for induction, and initial Bishop's scores. There were significant change in the Bishop's score in the two groups (5.9 +/- 0.2 and 4.0 +/- 0.2, respectively, p < 0.001) but no inter group differences. Oxytocin induction or augmentation of labour occurred more in the catheter group (95%) than in the misoprostol group (43.3%) (p < 0.0001). Induction to delivery interval was significantly shorter in the misoprostol group than in the catheter group (8.7 +/- 2.4 vs 11.9 +/- 2.7 h p < 0.0001). There was no significant difference noted in the caesarean or other operative delivery rates among patients in the two treatment groups. There was a higher incidence of tachysystole and hyperstimulation in the misoprostol group than in the catheter group (p < 0.03). No differences were observed between groups for meconium passage, 1- or 5-min Apgar scores < 7 and admission into the neonatal intensive care unit. In conclusion, the maternal and perinatal outcomes in this study have shown no difference confirming the efficacy and safety of both methods, however we observe a decrease in the induction-to-delivery interval when misoprostol is used for this purpose.

Induction of labor

The rate of labor induction continues to rise significantly in the United States because of a growing use of labor induction for postterm pregnancies and elective induction of labor. Although different types and doses of prostaglandins used for cervical ripening often initiate uterine activity, the principal role of these agents is to soften the unripe cervix independent of uterine activity. Several systematic reviews with meta-analyses have shown that prostaglandins are superior to placebo and oxytocin alone in ripening of the cervix. Numerous studies and meta-analyses have assessed misoprostol's efficacy and safety as a labor induction agent. The most appropriate dose and route of administration has not yet been confirmed.

Labor induction in women with an unfavorable Bishop score: randomized controlled trial of intrauterine Foley catheter with concurrent oxytocin infusion versus Foley catheter with extra-amniotic saline infusion with concurrent oxytocin infusion

OBJECTIVES

This study was undertaken to determine whether the addition of extra-amniotic saline infusion improves the efficacy of the Foley catheter in women undergoing cervical ripening and induction of labor with an unfavorable cervical examination.

STUDY DESIGN

One hundred consenting women with a Bishop score less than 5 with singleton gestation, intact membranes, vertex presentation, who required induction of labor were randomly assigned to 2 groups: Foley alone (Foley, n=49) or to the Foley catheter with extra-amniotic saline infusion (EASI, 30 mL of NS per hour infused through the distal port of the Foley, n=51). All women received concurrent dilute oxytocin infusion per protocol. The primary analysis was intent to treat. Nonparametric tests were used as indicated.

RESULTS

At randomization, the groups were well balanced for potential confounders including: parity, gestational age, prior cesarean delivery, preeclampsia, mean dilation, effacement, and Bishop score. There were no differences between the groups for time to delivery (Foley 17.7 +/- 10.5 hours vs EASI 17.4 +/- 11.7 hours, P=.9), the proportion of women delivered before 24 hours (Foley 41/49 [84%] vs EASI 39/51 [77%], P=.37) or cesarean rates (Foley 9/49 [17.7%] vs EASI 9/51 [18.4%], P=.92). There were also no differences in complications, including chorioamnionitis, endometritis, and neonatal morbidity.

CONCLUSION

EASI does not increase the efficacy of cervical ripening and induction of labor with a Foley catheter and concurrent oxytocin infusion.

Increased rates of chorioamnionitis with extra-amniotic saline infusion method of labor induction

OBJECTIVE

Extra-amniotic saline infusion has been shown to be equal to or more efficacious than misoprostol, laminaria, dinoprostone, and prostaglandin estradiol for cervical ripening and labor induction. Because of the introduction of a foreign body into the uterus, extra-amniotic saline infusion may potentially cause increased rates of chorioamnionitis. This study examines the risk of chorioamnionitis with extra-amniotic saline infusion compared with other methods of induction and spontaneous labor.

METHODS

A retrospective analysis was performed based on deliveries at Bellevue Hospital Center, a tertiary-care facility, from August 2000 to December 2002. Three groups were identified: extra-amniotic saline infusion, other methods of induction, and spontaneous labor. Differences in chorioamnionitis rates were analyzed by using analysis of variance and multivariable logistic regression as appropriate.

RESULTS

There were 625 charts evaluated: 171 extra-amniotic saline infusion, 190 other, and 264 with spontaneous labor. The rates of chorioamnionitis were 26.9%, 17.9%, and 13.3%, respectively. After adjusting for confounding variables, such as instrumentation, length of rupture, and number of exams, subjects who were induced with extra-amniotic saline infusion were significantly more likely to develop chorioamnionitis (relative risk = 2.2; 95% confidence interval 1.4, 4.0; P =.006).

CONCLUSION

Extra-amniotic saline infusion may be associated with a greater risk of chorioamnionitis when compared with other methods of labor induction. Given the increased risk of chorioamnionitis associated with extra-amniotic saline infusion, its use should be in the context of a careful assessment of the risks and benefits of various methods of labor induction.

LEVEL OF EVIDENCE

II-2

A comparison of vaginally administered misoprostol with extra-amniotic saline solution infusion for cervical ripening and labor induction

OBJECTIVE

The purpose of this study was to compare intravaginal misoprostol with extra-amniotic saline solution infusion with concomitant oxytocin for cervical ripening and labor induction in viable pregnancies.

STUDY DESIGN

Two hundred women with indications for labor induction and unfavorable cervices were assigned randomly to vaginal misoprostol or extra-amniotic saline solution infusion. Twenty-five micrograms of misoprostol was administered every 4 hours up to six doses, followed by intravenous oxytocin administration. Patients who had received extra-amniotic saline solution infusion also received intravenous oxytocin along with a maximum 12-hour saline solution infusion through Foley catheters that were placed above the internal cervical os.

RESULTS

One hundred women were randomly assigned to misoprostol, and 100 women were assigned randomly to extra-amniotic saline solution infusion. The average interval from start of induction to vaginal delivery was longer in the misoprostol group (1323.3 +/- 700.3 minutes) than in the extra-amniotic saline solution infusion group (970.4 +/- 502.7 minutes; P =.006, log transformed data). Abnormal fetal heart rate tracings were found in 30% of the patients who received misoprostol and in 19% of the patients who received extra-amniotic saline solution infusion (relative risk, 1.6; 95% CI, 1.0-2.4; P =.05). There was more tachysystole in the misoprostol group (8%) than in the extra-amniotic saline solution infusion group (1%; P =.02). There were no differences in the routes of deliveries or neonatal outcomes between groups.

CONCLUSION

Extra-amniotic saline solution infusion with oxytocin administration appears more effective and is associated with fewer maternal complications than misoprostol for cervical ripening and labor induction.

Mechanical methods for induction of labour

BACKGROUND

Mechanical methods were the first methods developed to ripen the cervix or to induce labour. Devices which were used include various type of catheters and of laminaria tents, introduced into the cervical canal or into the extra-amniotic space. Mechanical methods were never completely abandoned, but were substituted by pharmacological methods during recent decades. Potential advantages of mechanical methods, compared with pharmacological methods, may include simplicity of preservation, lower cost and reduction of the side effects. However, special attention should be paid to contraindications (e.g. low-lying placenta), risk of infection and maternal discomfort when inserting these devices. This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology.

OBJECTIVES

To determine the effects of mechanical methods for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment, prostaglandins (vaginal, intracervical, misoprostol) and oxytocin.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group Trials Register, the Cochrane Controlled Trials Register and bibliographies of relevant papers. Last searched April 2001.

SELECTION CRITERIA

The criteria for inclusion were the following: (1) clinical trials comparing mechanical methods used for third trimester cervical ripening or labour induction with placebo/no treatment or other methods listed above it on a predefined list of labour induction methods; (2) random allocation to the treatment or control group; (3) adequate or unclear method for allocation concealment; (4) violations of allocated management not sufficient to materially affect conclusions; (5) clinically meaningful outcome measures reported; (6) data available for analysis according to the random allocation; (7) missing data insufficient to materially affect the conclusions.

DATA COLLECTION AND ANALYSIS

A strategy has been developed to deal with the large volume and complexity of trial data relating to labour induction. This involved a two-stage method of data extraction. The initial data extraction was done centrally, and incorporated into a series of primary reviews arranged by methods of induction of labour, following a standardised methodology. The data will be extracted from the primary reviews into a series of secondary reviews, arranged by category of woman.

MAIN RESULTS

In total, 58 studies were considered; 45 studies have been included and 13 were excluded. Studies generally included women with unfavourable cervix and intact membranes. Comparing mechanical methods with placebo/no treatment, only one study with 48 participants reported on vaginal delivery not achieved in 24 hours (69% with mechanical methods versus 77% with placebo/no treatment; relative risk (RR) 0.90; 95% confidence interval (CI): 0.64-1.26). Hyperstimulation with fetal heart rate changes was not reported. The risk of caesarean section, reported in six studies including 416 women, was similar between groups (34%; RR 1.00; 95% CI: 0.76-1.30). There were no reported cases of severe neonatal and maternal morbidity. Comparing mechanical methods with vaginal PGE2, only one trial (109 women) reported on vaginal delivery not achieved in 24 hours (73% versus 42%; relative risk (RR) 1.74; 95% CI: 1.21-2.49). Compared with intracervical PGE2, only one trial (100 women) reported on vaginal delivery not achieved in 24 hours (68% versus 40%; relative risk (RR) 1.70; 95% CI: 1.15-2.51). Compared with with misoprostol, the effectiveness of mechanical methods was similar (34% versus 30%; relative risk (RR) 1.15; 95% CI: 0.80-1.66). The use of mechanical method reduced the risk of hyperstimulation with fetal heart rate changes when compared with prostaglandins: vaginal PGE2 (0% versus 6%; RR 0.14; 95% CI: 0.04-0.53), intracervical PGE2 (0% versus 1%; RR 0.21; 95% CI: 0.04-1.20) and misoprostol (4% versus 9%; RR 0.41; 95% CI: 0.20-0.87). There was no difference in the risk of caesarean section between mechanical methods and prostaglandins. Serious neonatal (three cases) and maternal morbidity (one case) were infrequently reported. When compared with oxytocin, use of mechanical methods reduced the risk of caesarean section (4 trials; 198 women; 17% versus 32%; RR 0.55; 95% CI: 0.33-0.91). The likelihood of vaginal delivery in 24 hours and of hyperstimulation with fetal heart rate changes was not reported. There were no reported cases of serious maternal morbidity and severe neonatal morbidity was not reported. These results are similar whatever specific mechanical method was used, except with extra-amniotic infusion. When comparing extra-amniotic infusion with any prostaglandins, women were more likely to not achieve vaginal delivery within 24 hours (57% versus 42%; RR 1.33; 95% CI: 1.02-1.75), the risk of caesarean section was increased (31% versus 22%; RR 1.48; 95% CI: 1.14-1.90), without a reduction of the risk of hyperstimulation.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to evaluate the effectiveness, in terms of likelihood of vaginal delivery in 24 hours, of mechanical methods compared with placebo/no treatment or with prostaglandins. The risk of hyperstimulation was reduced when compared with prostaglandins (intracervical, intravaginal or misoprostol). Compared to oxytocin in women with unfavourable cervix, mechanical methods reduce the risk of caesarean section. There is no evidence to support the use of extra-amniotic infusion.

Labor induction

Labor induction has become commonplace in modern obstetrics. The increasing rate of labor induction has probably played a role in the increased rate of cesarean delivery observed in the United States during the past few decades. Clearly, the favorability of the cervix has a substantial impact on the potential success of any labor induction. Induction in the setting of an unfavorable cervix can result in prolonged induction, prolonged hospitalization, failed induction, and an increased cesarean delivery rate. In this modern era of healthcare reform and cost containment, the identification of therapeutic strategies to enhance the success and cost-effectiveness of labor induction are of great interest. Ongoing research is needed to advance our knowledge of the mechanisms of parturition and cervical ripening in order to direct interventions for labor induction more effectively.

A randomized trial of misoprostol versus extra-amniotic sodium chloride infusion with oxytocin for induction of labor

OBJECTIVE

Our purpose was to compare the efficacy and safety of misoprostol and extra-amniotic sodium chloride infusion with oxytocin for induction of labor.

STUDY DESIGN

This randomized trial compared two methods of labor induction in women requiring cervical ripening. One hundred twenty-three women undergoing labor induction with a Bishop score < or =5 were randomly selected to receive either misoprostol, 50 microg intravaginally every 4 hours, or extra-amniotic sodium chloride infusion. The primary outcome variable was the time interval from induction to vaginal delivery.

RESULTS

Sixty-one women received extra-amniotic sodium chloride infusion and 62 women received misoprostol. The mean time interval from the start of induction to vaginal delivery was 15.0 +/- 5.0 hours and 16.5 +/- 7.2 hours for the extra-amniotic infusion and misoprostol groups, respectively (P, not significant). The cesarean delivery rate was not significantly different between the 2 groups (32.8% for the extra-amniotic infusion group; 19.4% for the misoprostol group). Maternal and neonatal outcomes were similar between the 2 groups.

CONCLUSIONS

Both methods of induction are equally efficacious and result in similar maternal and neonatal outcomes.

Labor induction with misoprostol

Misoprostol, a prostaglandin E(1 ) analog, is widely used in the United States for cervical ripening and labor induction. Its use for these indications is not approved by the US Food and Drug Administration. The only Food and Drug Administration-approved indication in the product labeling is the treatment and prevention of intestinal ulcer disease resulting from nonsteroidal anti-inflammatory use. Multiple trials have proved that misoprostol is an effective agent for cervical ripening and labor induction in term pregnancy; however, investigations continue regarding the optimal dose, dosing regimen, and route of administration. Uterine contraction abnormalities are often found in association with higher misoprostol doses. Some trials also indicate increased frequencies of meconium passage, neonatal acidemia, and cesarean delivery for fetal distress in women receiving higher doses of misoprostol. Overall, most trials fail to demonstrate a significant change in the cesarean delivery rate with the use of this agent. Misoprostol is an effective agent for cervical ripening and labor induction when used in a judicious and cautious fashion.

Uterine rupture associated with the use of misoprostol in the gravid patient with a previous cesarean section

OBJECTIVE

Our purpose is to report our experience with uterine rupture in patients undergoing a trial of labor after previous cesarean delivery in which labor was induced with misoprostol. The literature on the use of misoprostol in the setting of previous cesarean section is reviewed.

STUDY DESIGN

This report was based on case reports, a computerized search of medical records, and literature review.

RESULTS

Uterine rupture occurred in 5 of 89 patients with previous cesarean delivery who had labor induced with misoprostol. The uterine rupture rate for patients attempting vaginal birth after cesarean section was significantly higher in those who received misoprostol, 5.6%, than in those who did not, 0.2% (1/423, P =.0001). Review of the literature reveals insufficient data to support the use of misoprostol in the patient with a previous cesarean delivery.

CONCLUSION

Misoprostol may increase the risk of uterine rupture in the patient with a scarred uterus. Carefully controlled studies of the risks and benefits of misoprostol are necessary before its widespread use in this setting.