Abstract
Objective
To study the association between the method of induction of labor (IOL) and perinatal outcomes, among women undergoing labor after cesarean (LAC) with no prior vaginal delivery.
Method
A retrospective study including all women with no prior vaginal delivery undergoing IOL for LAC between March 2011 and January 2021. Oxytocin administration following prelabor rupture of membranes (PROM), oxytocin administration only, extra‐amniotic balloon, and amniotomy were compared.
Results
Overall, 363 women met the inclusion criteria: extra‐amniotic balloon (157, 43.3%), oxytocin following PROM (95, 26.2%), amniotomy (72, 19.8%), and oxytocin (39, 10.7%). LAC success rate did not differ among study groups (P = 0.114), varying between 62.1% and 79.5%. There were three uterine ruptures (0.8%) in the entire cohort. The rate of uterine rupture, postpartum hemorrhage, and the composite of both were similar in all study groups. Neonatal outcomes did not differ between study groups, with composite adverse neonatal outcomes varying between 7.4% in the oxytocin following PROM to 1.9% in the extra‐amniotic balloon group (P = 0.141). The following factors were independently associated with LAC success: taller maternal height, lower body mass index, earlier gestational age, and epidural analgesia.
Conclusions
All examined IOL methods with an unfavorable cervix carried similar outcomes. The clinical practice should be individualized.
Keywords: cesarean birth, induction of labor, labor after cesarean, outcome, vaginal birth after cesarean
Synopsis
All induction of labor methods in labor after cesarean with no previous vaginal delivery carry similar outcomes.
1. INTRODUCTION
The current global cesarean delivery (CD) rate is approximately 21%, and it is estimated that by 2030 the global CD rate will reach 30%. 1 The prior dogma of “once a cesarean always a cesarean” has been replaced by current practice guidelines that advocate for a trial of labor after cesarean (LAC) among women who had a prior CD. 2 , 3
Induction of labor (IOL) for various indications is a common obstetric intervention, with an estimated rate ranging between approximately 5% and 40% in different countries. 4 It is thought that the rate of IOL in women with a previous CD does not differ from that of other parturients. 5 , 6
Although LAC is generally encouraged, it carries risks including uterine rupture, a potential obstetric catastrophe that is estimated to occur in 8:1000 of spontaneous LAC. 7 , 8 , 9 , 10 IOL in LAC is also associated with an increased risk for uterine rupture. 11 Moreover, IOL is associated with a decreased rate of successful LAC. 2 Therefore, while in general spontaneous LAC is preferred, in many clinical scenarios that require delivery, the patient is faced with a choice of IOL LAC or repeat CD. If IOL is chosen, the clinician must choose the best method for the patient. Therefore, it is important to examine the association of the various methods of IOL with various LAC outcomes, including success rate and maternal and neonatal morbidity. Literature regarding this topic lacks randomized controlled trials, and mainly includes studies underpowered to detect clinically relevant differences. 6
The purpose of this study was to evaluate the association between the method of IOL and maternal and neonatal outcomes among women undergoing LAC with no prior vaginal delivery.
2. MATERIALS AND METHODS
2.1. Patients
This is a retrospective study. The study cohort consisted of women undergoing a LAC with one prior CD and no prior vaginal delivery (P1CS1). All deliveries occurred at the one tertiary medical center in Israel, from March 2011 to January 2021.
Inclusion criteria included all of the following: a singleton gestation, cephalic presentation, pregnancy duration more than 23+6 weeks, and a prior low transverse uterine incision. We allocated the study cohort into four groups according to IOL method: oxytocin administration following prelabor spontaneous rupture of membranes (PROM), oxytocin administration only, extra‐amniotic balloon, and amniotomy. Interpretation of the results was performed according to the initial methods of IOL. We excluded women with more than one prior CD. We included fetuses of all growth centiles. The study cohort did not include any fetuses with major genetic abnormalities. We did not exclude macrosomic fetuses or women with gestational or other comorbidities such as diabetes or hypertensive disorders.
The primary outcome of the study was the mode of delivery, including vaginal birth after cesarean (VBAC) and unplanned repeat CD. VBAC included spontaneous vaginal and operative vaginal deliveries (vacuum‐assisted and forceps). Secondary outcomes were adverse maternal and neonatal outcomes.
2.2. Methods of IOL
All women with a previous CD admitted for IOL were examined and counseled by a senior obstetrician. All data presented in the current study are collected retrospectively. IOL method is at the discretion of the senior experienced obstetrician who examined the parturient after cervical digital examination and full obstetric evaluation including ultrasound examination and fetal heart rate tracing (biophysical profile).
2.3. Oxytocin administration only and following PROM
Among women undergoing LAC, oxytocin is administrated at a rate of 1 mU/min, with gradual increase of 1–1.25 mU/min every 30 min to a maximal dose of 15 mU/min. Following PROM, our institution's protocol requires conservative management for 48 h. In cases in which spontaneous onset of labor does not start within 48 h, oxytocin administration is begun.
2.4. Extra‐amniotic balloon
We insert a 22F Foley catheter through the cervix under direct visualization with the use of a sterile vaginal speculum. Before insertion, the cervix is cleansed with aseptic solution. Once the catheter passes the internal os, the balloon is inflated with 40–60 ml 0.9% NaCl solution, and the external end of the catheter is taped to the inner part of the thigh.
2.5. Amniotomy
Following a cervical digital examination, when cervical dilation is assessed to be sufficient for amniotomy (e.g., usually more than 1.5 cm), the membranes are punctured with a crochet‐like handled hook during a vaginal digital examination. Amniotic fluid emerging serves as evidence for a successful amniotomy. Amniotomy time and amniotic fluid color are recorded at real time.
2.6. Data collection
We collected the following variables: maternal characteristics including maternal age, smoking and immigration status, height and calculated body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) before delivery, diabetic and hypertensive disorders; prior CD characteristics including gestational age at delivery, indications for the prior CD, cervical dilation and birth weight at prior CD; current delivery characteristics including gestational age at delivery, sonographic estimated fetal weight, inter‐delivery interval from prior CD, cervical dilation and effacement at admission LAC, epidural analgesia administration, presence of meconium‐stained amniotic fluid and intrapartum fever; mode of delivery; maternal outcomes including uterine rupture and postpartum hemorrhage; neonatal characteristics and outcomes including birth weight, birth weight centile, APGAR scores at 1 and 5 min, arterial pH, neonatal intensive care unit admission and need for mechanical ventilation.
Hypertensive disorders of pregnancy were defined according to the American College of Obstetricians and Gynecologists, integrating gestational hypertension and pre‐eclampsia. 12 Diabetic disorders were defined as either pregestational diabetes, in accordance with the American Diabetes Association criteria, 13 or gestational diabetes mellitus, using the diagnostic thresholds established by Carpenter and Coustan. 14 Intrapartum fever was defined as temperature of at least 38.0°C that persisted for at least 30 minutes or a single oral temperature of 39°C. 15 , 16 Birth weight centiles were calculated using local, population‐based live‐born infants' birth weight curves. 17 Postpartum hemorrhage was defined as any transfusion of packed red blood cells. No cases of severe anemia without blood transfusion were included in postpartum hemorrhage cases.
The composite maternal outcome was defined as the presence of either uterine rupture or postpartum hemorrhage.
The composite neonatal outcome was defined as the presence of any of the following: APGAR scores below 5 at 1 min or below 7 at 5 min, admission to neonatal intensive care unit, or neonatal mechanical ventilation.
We compared characteristics and outcomes of the four groups according to IOL method. We further dichotomized the cohort into two groups: VBAC versus unplanned repeat CD.
2.7. Statistical analysis
Univariable analysis was performed with the χ2 test or Fisher exact test as appropriate for categorical variables. When statistical significance was reached, for the purpose of identifying which pairs of groups were significantly different, we used the pairwise comparison of proportions using the Bonferroni correction. When comparing more than two groups, for continuous variables we used the one‐way analysis of variance test with post hoc Tukey's honestly significant difference for normally distributed data, and Games Howell for nonparametric data as appropriate. For dichotomized comparisons, we used the Student t test for analysis of continuous variables with normal distribution and the Mann–Whitney U test for analysis of continuous variables with skewed distribution. Multivariable logistic regression analysis was used to adjust for potential confounding factors for successful LAC, and results are reported as odds ratios and 95% confidence intervals. Potentially associated factors included those identified by univariate analysis (P < 0.05). A two‐sided P value less than 0.05 indicated statistical significance. The data were analyzed using SPSS version 27 (IBM Corp).
2.8. Ethics statement
The study protocol was approved by the Sheba Medical Center review board (7145‐20‐SMC, 30/09/2020).
3. RESULTS
Overall, 363 women met the inclusion criteria and were grouped as follows: extra‐amniotic balloon (157, 43.3%), oxytocin following PROM (95, 26.2%), amniotomy (72, 19.8%), and oxytocin (39, 10.7%) (Figure 1).
FIGURE 1.
Schematic flow chart of patient inclusion in the study.
Table 1 presents a comparison of the study groups according to LAC induction method.
TABLE 1.
Characteristics of women undergoing LAC according to induction methods a
| Characteristics | Oxytocin following PROM (n = 95) | Oxytocin (n = 39) | Extra‐amniotic balloon (n = 157) | Amniotomy (n = 72) | P value b |
|---|---|---|---|---|---|
| Women | |||||
| Age, year | 33 ± 4.2 | 32 ± 3.9 | 31 ± 4.8 | 30 ± 4.8 | <0.001 (1 vs. 3,4) |
| Immigrant | 16 (16.8%) | 7 (17.9%) | 29 (18.5%) | 19 (26.4%) | 0.430 |
| BMI, predelivery | 28.5 ± 4.8 | 28.1 ± 4.1 | 29.4 ± 5.3 | 28.8 ± 5.2 | 0.409 |
| Height, cm | 163 ± 6.5 | 163 ± 6.1 | 163 ± 6.0 | 163 ± 5.7 | 0.853 |
| Weight gain, kg | 13 ± 5.7 | 13 ± 5.2 | 12 ± 5.7 | 13 ± 6.4 | 0.104 |
| Smoking | 5 (5.3%) | 2 (5.1%) | 6 (3.8%) | 1 (1.4%) | 0.602 |
| Diabetic disorder | 2 (2.1%) | 5 (12.8%) | 28 (17.8%) | 5 (6.9%) | 0.043 (1 vs. 3) |
| Hypertensive disorder | 1 (1.1%) | 4 (10.3% | 15 (9.6%) | 2 (2.8%) | 0.018 (1 vs. 3) |
| Previous delivery | |||||
| Gestational age at cesarean delivery, weeks | 38+1 ± 2+1 | 38+5 ± 2+2 | 37+3 ± 3+0 | 38+1 ± 2+3 | 0.028 (2 vs. 3) |
| Indication for cesarean delivery | |||||
| Other | 59 (62.1%) | 19 (48.7%) | 98 (62.4%) | 45 (60.9%) | |
| Fetal distress | 10 (10.5%) | 6 (15.4%) | 19 (12.1%) | 10 (13.9%) | |
| Arrest of labor | 26 (27.4%) | 14 (35.9%) | 40 (25.5%) | 17 (23.6%) | 0.764 |
| Elective cesarean delivery | 18 (22.5%) | 12 (34.3%) | 34 (25.6%) | 18 (30.5%) | 0.517 |
| Cervical dilation at delivery, cm | 3 ± 2.7 | 4 ± 3.4 | 2 ± 2.2 | 3 ± 2.8 | 0.037 |
| Second stage | 1 (1.1%) | 4 (10.3%) | 1 (0.6%) | 2 (2.8%) | (2 vs. 3) |
| Birth weight, g | 3002 ± 612 | 3114 ± 713 | 2833 ± 815 | 2993 ± 610 | 0.082 |
| Current gestation | |||||
| Gestational age at LAC, week | 39 3/7 ± 1 5/7 | 40 °/7 ± 1 4/7 | 39 2/7 ± 2 4/7 | 40 2/7 ± 1 1/7 | 0.004 (4 vs. 1,3) |
| Sonographic estimated fetal weight, g | 3149 ± 461 | 3266 ± 401 | 3161 ± 544 | 3277 ± 366 | 0.223 |
| Inter‐delivery interval, year | 3 ± 0.6 | 3 ± 0.5 | 2 ± 0.6 | 2 ± 0.6 | 0.338 |
| Cervical dilation at admission, cm | 1 ± 0.8 | 2 ± 0.8 | 1 ± 0.6 | 2 ± 0.8 | <0.001 (All except 2 vs. 4) |
| Cervical effacement at admission, % | 70 ± 13 | 70 ± 10 | 60 ± 16 | 80 ± 11 | <0.001 (3 vs. all, 4 vs. 1) |
| Oxytocin administration | 91 (95.8%) | 38 (97.4%) | 97 (61.8%) | 22 (30.6%) | <0.001 (4 vs. 1–3, 3 vs. 1–2, 1 + 2 vs. 3,4) |
| Epidural analgesia | 77 (81.1%) | 33 (84.6%) | 136 (86.6%) | 67 (93.1%) | 0.166 |
| Meconium‐stained amniotic fluid | 17 (17.9%) | 5 (12.8%) | 29 (18.5%) | 24 (33.3%) | 0.020 |
| Intrapartum temperature > 38.0°C | 3 (3.2%) | 0 (0%) | 7 (4.5%) | 4 (5.6%) | 0.493 |
Abbreviations: LAC, labor after cesarean; PROM, prelabor rupture of membrane.
Data are presented as number (percentage) or mean ± standard deviation.
In brackets are the groups that differ significantly (P < 0.05) when 1 = oxytocin following PROM, 2 = oxytocin, 3 = extra‐amniotic balloon, and 4 = amniotomy.
3.1. Maternal characteristics
The mean maternal age was higher in the oxytocin following PROM group compared with extra‐amniotic balloon and amniotomy (33 vs. 31 and 30 years old, respectively, P < 0.001). The proportion of women with diabetic disorders and hypertensive disorders was higher in the extra‐amniotic balloon group compared with women induced by oxytocin following PROM (17.8% vs. 2.1% and 9.6% vs. 1.1%, P = 0.043 and P = 0.018, respectively).
3.2. Previous cesarean characteristics
Mean pregnancy duration at previous CD was higher in the oxytocin group compared with the extra‐amniotic balloon group (38+5 vs. 37+3 weeks, P = 0.028). Cervical dilation at previous CD was higher in the oxytocin group compared with the extra‐amniotic balloon group (mean 4 vs. 2 cm, P = 0.037).
3.3. LAC characteristics
Mean pregnancy duration at LAC was higher in the amniotomy group compared with the oxytocin following PROM and extra‐amniotic balloon groups (40+2 vs. 39+3 vs. 39+2 weeks, P = 0.004). Cervical effacement at admission was lower in the extra‐amniotic balloon group (60% vs. 70%–80%, P < 0.001).
Oxytocin administration at any time was lower in the amniotomy group (30.6% vs. 61.8%–100%, P < 0.001). The proportion of meconium‐stained amniotic fluid was higher in the amniotomy group (33.3% vs. 12.8%–18.5%, P = 0.020).
Table 2 presents the LAC, maternal and neonatal outcomes according to the induction method.
TABLE 2.
LAC outcomes of women and neonates according to induction method a
| Characteristics | Oxytocin following PROM (n = 95) | Oxytocin (n = 39) | Extra‐amniotic balloon (n = 157) | Amniotomy (n = 72) | P value b |
|---|---|---|---|---|---|
| Delivery outcomes | |||||
| Mode of delivery | |||||
| Spontaneous | 46 (48.4%) | 22 (56.4%) | 80 (51.0%) | 37 (51.4%) | 0.147 |
| Vacuum | 11 (11.6%) | 7 (17.9%) | 15 (9.6%) | 15 (20.8%) | |
| Forceps | 2 (2.1%) | (5.1%) | 3 (1.9%) | 0 (0%) | |
| Cesarean | 36 (37.9%) | 8 (20.5%) | 59 (37.6%) | 20 (27.8%) | 0.114 |
| Indications | |||||
| Non reassuring fetal status | 19 (20.0%) | 2 (5.1%) | 30 (19.1%) | 14 (19.4%) | 0.180 |
| Dystocia | 9 (9.5%) | 4 (10.3%) | 24 (15.3%) | 3 (4.2%) | 0.085 |
| Maternal outcomes | |||||
| Uterine rupture | 1 (1.1%) | 0 (0%) | 2 (1.3%) | 0 (0%) | 0.713 |
| Postpartum hemorrhage | 8 (8.5%) | 0 (0%) | 8 (5.2%) | 6 (8.7%) | 0.219 |
| Composite maternal | 10 (10.5%) | 0 (0%) | 13 (8.3%) | 9 (12.5%) | 0.145 |
| Neonatal outcomes | |||||
| Birth weight, g | 3209 ± 472 | 3277 ± 435 | 3140 ± 637 | 3420 ± 403 | 0.003 (3 vs. 4) |
| Higher birth weight in LAC than previous birth weight | 64 (67.4%) | 25 (64.1%) | 98 (62.4%) | 57 (79.2%) | 0.091 |
| Weight centile | 55 ± 24 | 53 ± 26 | 62 ± 80 | 69 ± 81 | 0.470 |
| APGAR 1 min < 5 | 2 (2.1%) | 0 (0%) | 3 (1.9%) | 1 (1.4%) | 0.833 |
| APGAR 5 min < 7 | 0 (0%) | 0 (0%) | 1 (0.6%) | 0 (0%) | 0.752 |
| pH arterial < 7 | 1 (1.1%) | 0 (0%) | 1 (0.6%) | 0 (0%) | 0.784 |
| Neonatal intensive care unit admission | 6 (6.3%) | 1 (2.6%) | 2 (1.3%) | 2 (2.8%) | 0.159 |
| Mechanical ventilation | 2 (2.1%) | 0 (0%) | 0 (0%) | 1 (1.4%) | 0.283 |
| Composite neonatal | 7 (7.4%) | 1 (2.6%) | 3 (1.9%) | 2 (2.8%) | 0.141 |
Abbreviations: LAC, labor after cesarean; PROM, prelabor rupture of membranes.
Data are presented as number (percentage) or mean ± standard deviation.
In brackets are the groups that differ significantly (P < 0.05) when 1 = oxytocin following PROM, 2 = oxytocin, 3 = extra‐amniotic balloon, and 4 = amniotomy.
3.4. LAC success
The LAC success rate did not differ among study groups (P = 0.114), varying from 79.5% in the oxytocin group to 62.1% in the oxytocin following PROM group. The indication for unplanned repeat CD also did not differ between groups.
3.5. Maternal outcome
There were three uterine ruptures (0.8%) in the entire cohort. The rate of uterine rupture, postpartum hemorrhage, and the composite of both were similar in all study groups (Table 2).
3.6. Neonatal outcomes
Neonatal outcomes did not differ between study groups, with composite adverse neonatal outcomes ranging from between 7.4% in the oxytocin following PROM to 1.9% in the extra‐amniotic balloon group (P = 0.141).
3.7. Comparison of LAC success versus failure
Table 3 presents univariate analysis in relation to LAC success. The following factors were associated with LAC success: taller maternal height, lower maternal BMI, lower gestational age, and epidural analgesia administration. The following factors were negatively associated with LAC success: maternal hypertensive disorder, and labor arrest at previous CD. The method of induction was not associated with LAC success.
TABLE 3.
Maternal, delivery, and neonatal characteristics of successful versus failed LAC a
| Characteristics | Success (n = 240) | Failure (n = 123) | P value |
|---|---|---|---|
| Women | |||
| Age, year | 31 ± 4.6 | 31 ± 4.7 | 0.257 |
| BMI, predelivery | 28.1 ± 4.6 | 30.5 ± 5.5 | <0.001 |
| Height, cm | 164 ± 6.0 | 161 ± 6.0 | <0.001 |
| Weight gain, kg | 13 ± 5.6 | 12 ± 6.3 | 0.636 |
| Hypertensive disorder | 32 (2.0%) | 22 (4.3%) | 0.003 |
| Diabetic disorder | 26 (10.8%) | 14 (11.4%) | 0.874 |
| Hypertensive disorder | 12 (5.0%) | 10 (8.1%) | 0.237 |
| Previous delivery | |||
| Gestational age at cesarean delivery, week | 37+6 ± 2+3 | 38+2 ± 2+3 | 0.224 |
| Indication for cesarean delivery | |||
| Other | 165 (68.8%) | 56 (45.5%) | |
| Fetal distress | 20 (8.3%) | 25 (20.3%) | |
| Arrest of labor | 55 (22.9%) | 42 (34.1%) | <0.001 |
| Cervical dilation at delivery, cm Second stage | 3 ± 2.76 (2.5%) | 3 ± 2.62 (1.6%) | 0.9710.722 |
| Birth weight, g | 2939 ± 725 | 2941 ± 717 | 0.981 |
| Current gestation | |||
| Gestational age at LAC, week | 39+3 ± 2+2 | 39+6 ± 1+4 | 0.033 |
| Inter‐delivery interval, year | 2 ± 0.6 | 2 ± 0.6 | 0.909 |
| Cervical dilation at admission, cm | 1 ± 0.9 | 1 ± 0.9 | 0.588 |
| Cervical effacement at admission | 70 ± 15 | 70 ± 15 | 0.201 |
| Oxytocin administration | 166 (69.2%) | 82 (66.7%) | 0.628 |
| Epidural analgesia | 227 (94.6%) | 86 (69.9%) | <0.001 |
| Intrapartum temperature > 38.0°C | 9 (3.8%) | 5 (4.1%) | >0.99 |
| Mode of induction | |||
| Oxytocin following PROM | 59 (24.6%) | 36 (29.3%) | |
| Oxytocin | 31 (12.9%) | 8 (6.5%) | |
| Extra‐amniotic balloon | 98 (40.8%) | 59 (48.0%) | |
| Amiontomy | 52 (21.7%) | 20 (16.3%) | 0.114 |
| Newborns | |||
| Birth weight, g | 3195 ± 50 | 3293 ± 526 | 0.107 |
| Heavier than previous cesarean delivery | 157 (65.4%) | 87 (70.7%) | 0.307 |
| Weight centile | 58 ± 49 | 66 ± 88 | 0.319 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by the square of height in meters); LAC, labor after cesarean; PROM, prelabor rupture of membranes.
Data are presented as number (percentage) or mean ± standard deviation.
Table 4 presents multivariable regression analysis. The following factors were independently associated with LAC success: taller maternal height, lower BMI, earlier gestational age, and epidural analgesia.
TABLE 4.
Multivariate regression analysis of factors associated with LAC success
| Characteristics | Adjusted OR (95% CI) | P value |
|---|---|---|
| Height, cm | 1.08 (1.03–1.13) | <0.001 |
| BMI, predelivery | 0.90 (0.86–0.95) | <0.001 |
| Hypertensive disorder | 0.49 (0.17–1.40) | 0.187 |
| Arrest of labor at primary cesarean delivery | 0.56 (0.32–0.98) | 0.43 |
| Gestational age at LAC, week | 0.97 (0.95–0.99) | 0.018 |
| Epidural analgesia | 9.18 (4.25–19.82) | <0.001 |
| Cervical dilation, cm | 1.17 (0.89–1.53) | 0.239 |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by the square of height in meters); CI, confidence interval; LAC, labor after cesarean; OR, odds ratio.
Tables S1 and S2 present multivariate analysis of factors associated with LAC success at various cervical dilations at admission. Maternal height and epidural analgesia were the only factors independently associated with LAC success at all cervical dilations. Method of IOL was not associated with LAC success in this analysis.
4. DISCUSSION
In this study of four IOL methods among women undergoing LAC, IOL methods were not associated with VBAC rates. Adverse maternal and neonatal outcomes, including uterine rupture rate, did not differ in the various methods of IOL either.
Interestingly, the rate of unplanned CD in the extra‐amniotic balloon group in our study (37.6%) was similar to a recent Finnish study (38.0%). 18 However, it was lower than another study and a systematic review, which demonstrated an unplanned CD rate of 43.6%. 19 , 20 Of note, those studies included heterogeneous populations with some patients having had prior vaginal deliveries, highlighting the relatively high success rate of LAC after IOL with extra‐amniotic balloon in our cohort.
The rate of uterine rupture in our study (0.8% in the whole cohort and 1.3% in the extra‐amniotic balloon group) was similar to rates reported in the literature (0.3%–1.2%). 18 , 20 However, as this is a rare event that necessitates adequate statistical power to be assessed, it is difficult to draw conclusions. A recent Swedish report published a 5% uterine rupture rate of LAC undergoing induction by prostaglandins, and 2.2% with extra‐amniotc balloon. 21 Importantly, the 0.8% uterine rupture rate in our study is similar to the uterine rupture rate of LAC with a spontaneous onset of delivery. 2 This is a reassuring message that must be included when counseling women who may be opting for an IOL.
Interestingly, oxytocin administration at any stage of delivery was low in the amniotomy group in our study in comparison to the reported rate of oxytocin augmentation in the literature (68.4%–85.3%). 18 , 20 Similarly, oxytocin was only used in 61.8% of women in the extra amniotic balloon group (61.8%). As uterine rupture is more frequent in the active phase of labor and following uterine contractions, which are provoked by oxytocin, this information could be provided for women when counseling for IOL method, advocating for amniotomy and extra‐amniotic balloon.
A previous French study randomized IOL in LAC to extra‐amniotic balloon and to oxytocin and extra‐amniotic balloon. 22 Of note, that trial is one of the only randomized controlled trials addressing this issue. The study underlined exceptionally low LAC success rates (37%–50%) with a higher rate in the extra‐amniotic balloon group and no complete uterine ruptures. Importantly, approximately 20% of women included in the study had a prior vaginal delivery.
Recently there has been increasing interest in the use of extra‐amniotic balloon for IOL in LAC 23 , 24 with studies reporting favorable outcomes. A Cochrane review 6 evaluated different methods of IOL as well. Of a total of eight studies included in that review, extra‐amniotic balloon was found to carry similar outcomes compared with oxytocin.
Amniotomy, when studied for IOL among the general population, has been found to be an expeditious method with no added neonatal morbidity 25 and no additional risk of unplanned CD. 26 Although the literature regarding amniotomy for IOL in LAC is underreported, it seems appropriate to deduce that this method might be applicable and acceptable as well, with no added morbidity in LAC. It is important to acknowledge that amniotomy can only be performed when there is adequate cervical dilation, and that extra‐amniotic balloon could not be performed when cervical dilation is above 2–3 cm. Therefore, the population included in our study is heterogeneous. However, we provide an analysis of no cervical dilation and cervical dilation of 1 cm or more to try and mitigate this caveat.
Our study has limitations. Its main obvious limitation is the retrospective nature with no prospective randomization. We cannot account for the reasons the various methods of IOL were chosen by the senior obstetricians, although we did analyze cervical dilation with this regard. A second notable caveat is the limited sample size that might be underpowered to assess statistical significance of rare maternal and neonatal outcomes. We did not assess the time interval from IOL to delivery, which is another desirable outcome. Furthermore, induction of LAC by prostaglandins is not performed in our country of practice, and we did not assess other methods of cervical ripening such as laminaria insertion. However, we were able to compare four different study groups and perform a regression analysis to control for confounders in the analysis of LAC success. Finally, several outcomes examined in our study are of questionable clinical significance (e.g., APGAR score at 1 min).
In summary, all IOL methods in LAC with no prior vaginal delivery with an unfavorable cervix carried similar outcomes. The clinical practice should be individualized per woman.
AUTHOR CONTRIBUTIONS
RM and GL: contributed to conceptualization, formal analysis, investigation and methodology, writing—original draft, and writing—review and editing. AT and YB contributed to data acquisition, investigation, and drafting and revising.
CONFLICT OF INTEREST
The authors have no conflicts of interest.
Supporting information
Table S1
Table S2
Levin G, Tsur A, Burke YZ, Meyer R. Methods of induction of labor after cesarean with no prior vaginal delivery—Perinatal outcomes. Int J Gynecol Obstet. 2023;160:612‐619. doi: 10.1002/ijgo.14318
DATA AVAILABILITY STATEMENT
Research data are not shared.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Table S1
Table S2
Data Availability Statement
Research data are not shared.