Ripening the highly unfavorable cervix with extra-amniotic saline instillation or vaginal prostaglandin E2 application

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.

Extra-amniotic Foley catheter and prostaglandin E(2) gel for cervical ripening at term gestation

OBJECTIVE

This study evaluated the efficacy of intravaginal prostaglandin E(2) gel in comparison with that of a Foley catheter for cervical ripening and induction of labor.

STUDY DESIGN

Consecutive patients with unfavorable cervix requiring preinduction cervical ripening and induction of labor at term gestation were asked to participate in the study. One hundred and two patients were assigned to treatment with intravaginal prostaglandin E(2) gel (group 1) and 122 patients underwent the placement of an intracervical Foley catheter (group 2). After a maximum of three applications of intravaginal prostaglandin E(2) gel (18h) or after 18h from Foley catheter insertion oxytocin was administered to patients not in active labor. Labor profiles and pregnancy and neonatal outcome were compared between groups.

RESULTS

The groups were comparable in term of demographic characteristics, indications for induction of labor, Bishop score at admission. The induction to labor time and the induction to delivery time were similar between groups. The cesarean sections rate was higher in group 1 than in group 2 (26.5 versus 14.7%, P<0.05). This remained significant when the analysis was restricted to nulliparous patients (32.3 versus 14.2%). The incidence of urinary tract infections, chorioamnionitis, and febrile morbidity was similar between groups.

CONCLUSION

For preinduction cervical ripening, the Foley catheter is a valid alternative to the application of intravaginal prostaglandin E(2) gel and it is associated with a lower cesarean rate in nulliparous women.

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.

Cervical ripening

Induction of labor is indicated when the benefits to either the mother or the fetus outweigh the benefits of continuing the pregnancy. The state of the cervix is clearly related to the success of labor induction and the duration of labor. In cases of unfavorable cervices, physicians usually use a ripening agent before inducing labor. Unfortunately, as reviewed in this article, the ideal ripening agent is not found yet. No method of cervical ripening has shown a consistent and significant reduction in CS rate. In fact, women with the most unfavorable cervices (Bishop score, < or = 2) still face high rates of induction failure and CS.

Ripening of the unfavorable cervix with extraamniotic catheter balloon: clinical experience and review

The use of an extraamniotic catheter balloon, inflated above the internal cervical os, has been advocated as a nonpharmacological, mechanical method of cervical ripening before induction of labor. Additional measures may include applying traction on the catheter, or the infusion of normal saline (1 ml/min) via the catheter's port into the extraamniotic space. The results of catheter balloon cervical ripening are reviewed from 13 published reports and a departmental series of 190 pregnancies with unfavorable cervix, encompassing nearly 1000 patients. A mean change in cervical score of at least 3 points, was noted in most studies after balloon expulsion or removal. The present series and other studies suggest that oxytocin use for induction and/or augmentation of labor is increased after balloon ripening, compared with its use in spontaneous labor or after cervical ripening by prostaglandins. In 11 studies, catheter balloon ripening was compared with cervical ripening by other mechanical, or pharmacological (i.e., oxytocin or prostaglandins) methods. Of these, eight were prospective and randomized-controlled and three were case-controlled studies. It is suggested that ripening efficacy by catheter balloon is similar, or better, than other methods; but there is no significant difference in the mode of delivery or perinatal outcome. This review also suggests that cervical ripening with extraamniotic catheter balloon has the advantages of simplicity, low cost, reversibility, and lack of systemic or serious side effects.

Induction of labour by balloon catheter with extra-amniotic saline infusion (BCEAS): a randomised comparison with PGE2 vaginal pessaries

OBJECTIVE

A new method for induction of labour--balloon catheter with extra-amniotic saline infusion (BCEAS)--is evaluated in randomised comparison with prostaglandin E2 (PGE2) in vaginal pessaries.

STUDY GROUP

One-hundred and nine pregnant women with unfavourable cervices.

MAJOR OUTCOME MEASURES

The efficiency of inducing vaginal delivery and the level of 'disadvantages following induction of labour' (DisFIL scorings).

RESULTS

Overall, BCEAS was less efficient inducing vaginal delivery than vaginal PGE2 (P < 0.01) because of a significant difference among parous women (P < 0.01). In the (larger) primiparous women group, and particularly in the subgroup of these having very low pelvic scores (Lange score, < or = 3), the efficiencies of the two methods were equal (P = 0.06) and P = 0.55, respectively). The levels of DisFIL scorings were not significantly different. However, higher rates of caesarean section followed BCEAS than PGE2 (29% and 10%, respectively; P < 0.05). Serious infectious complications were not recorded following BCEAS. No difference was apparent in the status of the neonates (judging from Apgar scores and umbilical artery pH and SBE). The women, delivering vaginally, commented the two methods equally favourably.

CONCLUSION

BCEAS was less efficacious than vaginal PGE2 pessaries, though among primiparous women, especially those with very unfavourable cervices, the difference was not significant. Further refinements of the method are suggested.

A simplified preinduction scoring method for the prediction of successful vaginal delivery based on multivariate analysis of pelvic and other obstetrical factors

Most of the popular preinduction scoring methods were created three decades ago, applied to selected populations and based on analysis of each factor separately. In order to overcome these limitations and to try and create a simple and reliable scoring method, 401 inductions of labor were analyzed. Failure was defined as delivery by cesarean section, regardless the indication. Results of multivariate analysis demonstrated that only two of the five factors used by Bishop's method were included (cervical dilatation and fetal head station). Gestational age and parity also constituted important factors and thus the new method incorporates these four factors. The variables among each factor were scored according to their relative risk, obtained from the analysis; dilatation 3 cm or more = 2, dilatation 1-2 cm = 1, fetal head station -1 cm or lower = 1, multiparity = 1, term delivery = 1, closed cervix = 0, station -2 cm or higher = 0, primiparity = 0 and non-term delivery = 0. Comparison of the suggested scoring method and Bishop's method demonstrated that in the low score category our method predicted more accurately cesarean section rate (44.7% and 27.6%, respectively). No difference was noted among the middle or high score groups. More studies among other populations may clarify whether our proposed method really overcomes other methods concerning simplicity, universality and predictability.

A randomized, double-blind trial of prostaglandin E2 gel for cervical ripening and meta-analysis

The ability of prostaglandin E2 to prepare the unripe cervix before an indicated labor induction is controversial. We therefore tested 100 pregnant women in a randomized, double-blind trial with intracervical prostaglandin E2 gel, 0.5 mg. The 53 women who received the placebo gel had an outcome similar to that of the 47 women who received the prostaglandin E2 gel. The mean change in cervical score, mean application-to-delivery interval, incidence of uncomplicated spontaneous labor, incidence of cesarean delivery for a failed induction, and the overall cesarean section rate were not significantly different for the two groups. A meta-analysis, incorporating 18 studies of 1811 patients who received a single application of at least 5 mg prostaglandin E2 gel intravaginally or 0.5 mg intracervically, demonstrated no significant decrease in the overall cesarean delivery rate (p = 0.85). We conclude that the use of single-dose intracervical prostaglandin E2 gel for cervical ripening has little effect on labor induction. Moreover, the use of single-dose intracervical or intravaginal prostaglandin E2 gel does not alter the incidence of cesarean delivery, even when large numbers of patients are analyzed by combining the results of similar reports.