In developed countries, approximately 20–25% of pregnant women undergo labor induction, many of whom require cervical ripening.1–4 The ARRIVE trial5 showed that, compared with expectant management, induction of labor at 39 weeks of gestation in low-risk nulliparous women resulted in significantly lower rates of cesarean delivery and hypertensive disorders of pregnancy. Despite these benefits, elective induction at 39 weeks of gestation was also associated with a 6-hour longer mean duration of stay in the labor and delivery unit.
Based on the results of this trial, both the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine opined that it is reasonable to offer elective induction at 39 weeks of gestation to nulliparous women.6,7 Thus, we anticipate that rates of labor induction will only continue to rise. This anticipated increase in labor induction, in combination with the increased stay in the labor and delivery unit, rising medical costs, and an increased emphasis on patient satisfaction, has led to a renewed interest in outpatient cervical ripening.4,8 The lower rates of uterine tachysystole and meconium-stained amniotic fluid associated with mechanical methods of cervical ripening make use of the Foley catheter particularly attractive for use in the outpatient setting.9–11 Indeed, the American College of Obstetricians and Gynecologists states that, “mechanical methods may be particularly appropriate in the outpatient setting.”3
Therefore, our objective was to evaluate use of a transcervical Foley catheter for outpatient cervical ripening in nulliparous women compared with standard inpatient management. We hypothesized that outpatient as compared with inpatient cervical ripening with a transcervical Foley catheter would shorten the time from hospital admission to delivery.
We performed an open-label randomized controlled trial in a single academic center. Institutional review board approval was obtained (IRB-300000831), and the study was registered on ClinicalTrials.gov (NCT03472937) before enrollment of the first patient. Safety was monitored by a Data and Safety Monitoring Board comprised of a neonatologist, a perinatologist, and an epidemiologist. Women were enrolled from May 2018 through October 2019.
All women receiving prenatal care within our system were identified and reviewed for eligibility before 36 weeks of gestation. Eligible women were contacted by telephone at approximately 37 weeks of gestation to introduce the study and confirm eligibility. Women were eligible for inclusion if they were nulliparous, were undergoing induction of labor, and were at least 18 years of age with a singleton fetus in the cephalic presentation. Additional inclusion criteria were a gestational age between 39 0/7 and 41 6/7 weeks at the time of enrollment, as determined by a dating ultrasound scan performed before 20 6/7 weeks of gestation. Women also had to have reliable transportation, access to a telephone, and live within 30 minutes of our hospital. Lastly, they had to have a modified Bishop score less than 5 and a maximum cervical dilation of 2 cm at the time of a cervical examination performed immediately before randomization. The components of the modified Bishop score included dilation, effacement, and station; a modified Bishop score less than 5 was modeled after the ARRIVE trial.5,12 As we intended to study a low-risk population, women who had prespecified medical or obstetric complications deemed inappropriate for outpatient cervical ripening were excluded. These conditions and their definitions are provided in Box 1.
- Fetal death
- Fetal anomalies: defined as the presence of a major fetal anomaly of any organ system*
- Fetal growth restriction: defined as an ultrasound-derived estimated fetal weight less than the 10th percentile for gestational age
- Suspected macrosomia: defined as an ultrasound-derived estimated fetal weight of 5,000 g or more in women without diabetes or 4,500 g or more in women with diabetes
- Oligohydramnios: defined as a single deepest vertical pocket less than 2 cm
- Polyhydramnios: defined as an amniotic fluid index of 24 cm or greater or a single deepest vertical pocket of 8 cm or greater
- Nonreassuring fetal status: defined as a biophysical profile result of 6/10 or less performed immediately before randomization
- Prior uterine surgery involving the myometrium: determined by chart review, including review of operative report when feasible
- Gestational hypertension or preeclampsia: diagnosed according to ACOG guidelines†
- Uncontrolled chronic hypertension: defined as the need for 2 or more antihypertensive medications
- Uncontrolled pregestational diabetes mellitus: defined as either less than 50% of patterned blood sugars at goal or the most recent hemoglobin A1c level of 7.0% or more
- White classification type C diabetes mellitus or higher: including White classification C, D, R, F, RF, H, or T‡
- Infection with hepatitis B or C or HIV: determined by review of the medical record
- Latex allergy
- Other conditions deemed by the attending physician to be unsuitable for outpatient cervical ripening
ACOG, American College of Obstetricians and Gynecologists; HIV, human immunodeficiency virus.
* Minor anomalies (eg, clubbed feet) or soft markers of fetal aneuploidy (eg, choroid plexus cysts, echogenic intracardiac focus) were eligible for inclusion, unless two or more of these minor anomalies were present, in which case the patient was not eligible.
† Gestational hypertension and preeclampsia. ACOG Practice Bulletin No. 202. American College of Obstetricians and Gynecologists. Obstet Gynecol 2019;133:e1–25.
‡ Women with well-controlled gestational diabetes (White classification A1 or A2) or well-controlled White classification B diabetes mellitus were eligible for inclusion.
Women who met eligibility criteria and who desired participation were scheduled for a study visit in our outpatient clinic at 39 0/7 weeks of gestation or more. At the time of the study visit, informed consent was obtained. The patient then underwent a biophysical profile, blood pressure evaluation, and cervical examination to ensure that all inclusion criteria were satisfied. Randomization was then performed in a 1:1 fashion with use of a computer-generated variable block randomization scheme, with block sizes of 2, 4, and 6. The randomization scheme was only available to the study statisticians. The randomization assignment was revealed online to study staff immediately after entry of screening information into the electronic database (Research Electronic Data Capture) and verification of eligibility.
Women randomized to outpatient cervical ripening had a 16-French Foley catheter placed immediately after randomization. The catheter was placed by a physician (resident, fellow, or attending) present in our outpatient clinic. Owing to the nature of our clinical schedules, this was not the same physician each time; however, all physicians were well trained in the placement of the balloon catheter. After application of a betadine solution to the cervix and vagina, the catheter was introduced just past the internal cervical os. The balloon was inflated with 30 mL of sterile water, and the catheter was then gently withdrawn so that the balloon applied pressure against the internal os. The catheter was then taped to the inner thigh. After transcervical Foley placement, at least 20 minutes of continuous fetal and uterine monitoring were performed. Women were directly admitted to the labor and delivery unit if amniotomy or significant vaginal bleeding occurred after transcervical Foley placement, if the fetal heart rate was nonreassuring, or if they had regular and painful contractions. This determination was made by the physician who was involved in placement of the transcervical balloon catheter, in consultation with the attending physician present in clinic. Otherwise, women were discharged home with labor precautions, as well as instructions that they could take acetaminophen, as needed, for pain relief. In addition, they were provided contact information for our 24-hour obstetric triage unit. Women were advised that they could remain at home if their transcervical catheter was expelled before their scheduled admission time, provided there were no other concerning signs or symptoms. They were instructed to record the time of expulsion of the catheter. All women were admitted to our labor and delivery unit the following day for their scheduled labor induction, at which time a repeat cervical examination was performed.
Women randomized to inpatient cervical ripening were discharged home from the clinic, again with labor precautions. They were also given a time to return to the hospital the following day for a scheduled induction. After admission, they were placed on continuous electronic fetal monitoring, and a physician confirmed fetal presentation. In addition, a repeat cervical examination was performed to ensure that cervical ripening was still needed. If so, a transcervical Foley catheter was placed in the same manner as described above.
In both groups, at the time of admission, oxytocin infusion was begun concurrently with the transcervical Foley catheter. This is our typical institutional practice, and concurrent use of both has been reported to result in a shorter time to delivery than sequential use.13,14 The transcervical Foley catheter could remain in place for up to 24 hours after initial placement. During this time, the patient’s labor nurse would periodically check for expulsion with gentle traction. If the Foley was still in place, the catheter was retaped to the inner thigh. Timing of amniotomy was at the discretion of the managing team. In accordance with our institutional protocol, the team was advised to avoid cesarean delivery for a diagnosis of failed induction until at least 18 hours of oxytocin use after amniotomy had elapsed.
Our primary outcome was the total duration of time from hospital admission to delivery. Admission, delivery, and discharge times were recorded by the hospital registrar. Several clinically relevant maternal and neonatal outcomes were selected a priori as secondary outcomes. These outcomes included chorioamnionitis, endometritis, cesarean delivery, postpartum hemorrhage, delivery within 24 hours of hospital admission, total hospital length of stay, and hospital readmission within 30 days of discharge. We also collected information on cervical examination at the time of admission, unscheduled hospital admissions or unscheduled visits to our obstetric triage unit before the time of scheduled admission, frequency of acetaminophen use after randomization but before hospital admission, calls to the obstetric triage unit, spontaneous rupture of membranes between randomization and hospital admission, duration of oxytocin infusion and maximum oxytocin rate (milliunits/min), duration of neuraxial anesthesia use, presence of heavy vaginal bleeding before delivery, meconium-stained amniotic fluid, time from rupture of membranes to delivery, highest maternal intrapartum temperature, and admission white blood cell count. Chorioamnionitis and endometritis were based on a diagnosis made by the managing physician team, typically requiring the presence of intrapartum or postpartum fever, respectively. Postpartum hemorrhage was defined as estimated blood loss more than 500 mL after vaginal delivery or more than 1,000 mL after cesarean delivery.15,16 Acetaminophen use was chosen as a proxy for pain in the outpatient setting. Heavy vaginal bleeding was defined by the presence of significant vaginal bleeding before delivery, as documented by either a nurse or physician. Neonatal outcomes included birth weight, 5-minute Apgar score less than 7, arterial umbilical cord blood gas pH less than 7.1, arterial umbilical cord blood gas base deficit greater than 12, and admission to the neonatal intensive care unit. In addition, we also assessed patient satisfaction by using a series of three questionnaires that the patient completed after delivery, but before hospital discharge. These totaled 17 questions and included the following surveys: Six Simple Questions,17 the Labor and Delivery Index,18 and a visual analog scale. The Six Simple Questions survey has been validated previously in pregnant women and consists of a series of questions that are designed to assess perceptions related to satisfaction with care. This survey is scored from 1 to 7 for each question, with 1 indicating “Strongly Disagree” and 7 indicating “Strongly Agree.” The Labor and Delivery Index questionnaire, also previously validated in pregnant women, addresses issues related to a patient’s overall experience of labor and delivery, assessing health care professional support, feelings of safety, and degree of worry. Answers range from 1 to 3 for each question, with 1 being the most positive response. Lastly, the visual analog scale assessed pain during labor and during the placement of the Foley catheter, as well as the likelihood of recommending the current method of labor induction to a friend or family member, with use of a scale that ranged from 0 to 100.
Medical records were reviewed for demographic data, medical and obstetric history, and intrapartum and postpartum events. All chart abstraction was performed by the primary author (E.B.A.), with data entered by this same author into an electronic database.
Based on previously collected data in our institution, the mean time to delivery for nulliparous women undergoing induction with a starting dilation of 2 cm or less is 19 hours (SD±10 hours). To have 80% power to demonstrate at least a 5-hour mean difference in time from admission to delivery assuming a two-sided alpha of 0.05, we planned to enroll 63 patients in each group, for a total sample size of 126. The 5-hour mean difference was selected to balance the desire to detect a clinically meaningful difference and sample size feasibility. All analyses were performed by the intention-to-treat principle. No interim analysis was performed. Patient characteristics and outcomes were compared by randomization group, using the following statistical tests as appropriate: t-test, Wilcoxon rank sum test, χ2 test, or Fisher exact test. Baseline characteristics that were significantly different at baseline, including maternal body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) and group B streptococcus (GBS) colonization were adjusted for, using linear regression to adjust for continuous outcomes and modified Poisson regression with robust standard errors to adjust for categorical outcomes. All analyses were performed using SAS 9.4.
Of 877 women screened, 548 were ineligible and 203 declined participation (Fig. 1). The remaining 126 women provided consent and were randomized, 63 in each group; 118 (94%) had successful placement of the transcervical Foley catheter. Two women in the outpatient group did not have successful placement of the Foley catheter. In both of these patients, the catheter was successfully placed on admission to the labor and delivery unit the following day. In the inpatient group, six women did not receive a transcervical Foley catheter—three women had a cervical examination at the time of admission that was too dilated to require cervical ripening; two women had rupture of membranes before catheter placement; one woman presented in labor before her scheduled admission time.
Baseline maternal and pregnancy characteristics (Table 1) were balanced between groups except for lower BMI (31±5.4 vs 34±7.5, P=.01) and a lower rate of GBS colonization (31% vs 54%, P=.01) in the outpatient group. The mean gestational age at randomization was 39.3 weeks in each group.
For the primary outcome (Table 2), women who had an outpatient transcervical Foley catheter for cervical ripening spent less time in the hospital before delivery (17.4±7.4 hours vs 21.7±9.1 hours), with a mean difference of 4.3 hours (95% CI 1.3–7.2, P<.01). The findings remained unchanged after adjusting for differences in BMI and GBS colonization (P=.03, beta coefficient −3.3, 95% CI −6.36 to −0.30). The proportion with time to delivery within 24 hours of hospital admission was also higher in the outpatient group (81% vs 65%, relative risk [RR] 1.2, 95% CI 1.0–1.5, P=.04). Despite these differences, the overall length of hospital stay was similar between groups (3.3±0.9 days vs 3.5±0.9 days, P=.27) (Table 2).
Women in the outpatient group were more likely to present before their scheduled time of admission than were women in the inpatient group—22% verus 5% (RR 4.7, 95% CI 1.4–15.4, P<.01), as shown in Table 2. In the outpatient group, reasons for presentation before the scheduled admission time were: active labor (n=3); discomforts related to the Foley catheter (n=2); regular uterine contractions but no cervical change (n=6); motor vehicle accident (n=1); and expulsion of the Foley catheter while at home (n=2). Notably, the two patients who were evaluated in the obstetric triage unit with discomforts from the Foley catheter had reassuring maternal and fetal evaluations and were comfortably discharged home with the Foley catheter still in place. Both women returned the following morning for their scheduled labor induction. All other women who presented early were admitted before their scheduled time. In women randomized to inpatient cervical ripening, three presented before their scheduled admission time for the following reasons: regular uterine contractions but without cervical change (n=1), spontaneous rupture of membranes (n=1), and heavy vaginal bleeding and a placental abruption (n=1). Women who had an outpatient intracervical Foley catheter were also more likely to contact our obstetric triage unit by phone (36% vs 3%, RR 11.2, 95% CI 2.7–45.5, P<.01), as well as to take acetaminophen for pain relief at home (53% vs 0%, P<.01). However, rates of spontaneous rupture of membranes before admission were not significantly different between groups (11% vs 16%, RR 0.7, 95% CI 0.3–1.7, P=.43) (Table 2).
Additional secondary outcomes are shown in Table 3. As expected, women who had outpatient cervical ripening had a more favorable cervical examination at the time of hospital admission, with a median cervical dilation of 3 cm compared with 1 cm (P<.01) and a median modified Bishop score of 3 compared with 1 (P<.01). Women who had outpatient cervical ripening had the transcervical Foley in place for a longer duration of time than those in the inpatient group (14.9±6.5 hours vs 5.2±2.3 hours, P<.01). However, many of the women who had outpatient cervical ripening presented for their scheduled admission and were found to have the Foley balloon in the vagina, with unrecognized expulsion. Twenty-five women in the outpatient group had unrecognized expulsion of the Foley balloon, and an additional 22 women had recognized expulsion of the balloon before admission; in only 16 women was the balloon still intracervical at the time of admission. Women who had outpatient cervical ripening required lower doses of oxytocin, a shorter duration of time of oxytocin infusion, and a shorter duration of neuraxial anesthesia use. Heavy vaginal bleeding occurred in one patient in each group, both of whom had a placental abruption. For the patient in the outpatient group, the placental abruption occurred after she was admitted for scheduled induction. Rates of meconium stained amniotic fluid, duration of rupture of membranes, and highest maternal temperature intrapartum were not different between groups. Chorioamnionitis occurred in 22% in the outpatient group and 13% in the inpatient group. This difference was not statistically different, with P=.16 (RR 1.8, 95% CI 0.8–3.9). After adjusting for BMI and GBS colonization, this remained nonsignificant, with an adjusted RR of 0.9 (95% CI 0.9–1.0). Despite no difference in infection, the mean admission white blood cell count was higher in the outpatient group (10.2±2.5×103/mm3 vs 8.2±2.3×103/mm3, P<.01), yet this value remained in the normal range in both groups. Cesarean delivery was not significantly different in the outpatient group (24% vs 32%, RR 0.8, 95% CI 0.4–1.3, P=.32). The most common indications for cesarean delivery were nonreassuring fetal status (n=19), followed by failed induction of labor (n=11). Operative vaginal delivery, postpartum hemorrhage, and endometritis were also not significantly different. Hospital readmission within 30 days of discharge only occurred in one patient who was in the inpatient group and was readmitted with diagnoses of endometritis and pyelonephritis.
Outpatient cervical ripening was not associated with an increase in adverse neonatal outcomes (Table 4). Lastly, the results of the patient satisfaction survey are presented in Appendix 1, available online at http://links.lww.com/AOG/C9. Women in both groups were overall satisfied with their care, with no significant differences in scores and safety concerns between groups.
In this randomized controlled trial, we found that women who had outpatient cervical ripening with a transcervical Foley catheter had a reduced time from hospital admission to delivery by more than 4 hours, likely due to a more favorable cervix at the time of hospital admission. However, they also had higher rates of unscheduled hospital admission. Although cesarean delivery and chorioamnionitis were not significantly different, this study was not powered to detect differences in these outcomes. Patient satisfaction scores were similar between groups.
Prior studies have reported that a difference of 3–3.5 hours less time in the labor and delivery unit may result in significant cost savings8,19,20; thus, we feel that our finding of 4.3 hours less time in the labor and delivery unit is clinically meaningful. This is further supported by our finding that women with outpatient ripening were more likely to deliver within 24 hours of hospital admission. However, we acknowledge that this difference is lower than the 5 hours that we selected as clinically meaningful for sample size computations. We note a lower SD than that used for the sample size calculation, enhancing the power to detect the smaller difference. We also acknowledge that, even with practical implementation, placement of an outpatient Foley catheter for cervical ripening will typically require an extra clinic visit. Despite this, we feel that our results remain clinically meaningful when viewed in the context of health care costs and similar patient satisfaction scores.
There have been few prospective studies evaluating use of the outpatient Foley catheter for cervical ripening. Sciscione et al21 published the first randomized trial in 2001, in which outpatient transcervical Foley catheter for cervical ripening was compared with standard inpatient management in both nulliparous and multiparous women. They demonstrated a decreased length of hospital stay (9.6 hours) in the outpatient group with no adverse maternal or neonatal outcomes. However, there was no difference between the two groups in the total time for induction of labor.
We chose to include only nulliparous women in our study, because a recent study from our institution evaluated outpatient cervical ripening with a transcervical Foley catheter in multiparous women and showed no difference in the time from admission to delivery.22 Further, we believe this question is of even greater clinical importance in nulliparous patients, who often have a less favorable cervix at the time of induction and a longer duration of the latent phase of labor compared with multiparas.23 We used a similar protocol and found several differences, likely reflecting differences in power, as well as the inherent differences in the two populations. The magnitude of the difference in unscheduled admission may reflect our conservative approach regarding instructions for re-presentation in the context of the study protocol. For example, despite instructions that women could remain at home if their Foley catheter was expelled, two women presented before their scheduled admission time for this reason. In the setting of routine care, we believe that early presentation for reasons such as this could be minimized.
Although our study was not powered to detect a difference in safety outcomes, our study and others are reassuring. In a retrospective study of 1,905 women with a transcervical Foley for cervical ripening, there were no cesarean deliveries for nonreassuring fetal status, placental abruption, or stillbirth from 2 hours postplacement until 6 am the following day (mimicking the timing of outpatient ripening).24 Similarly, a systematic review from 2018 reported adverse events from transcervical balloon placement to expulsion, the timeframe when patients would be in an outpatient setting. Discomfort was the most common adverse event, but other events were rare, with vaginal bleeding occurring in 0.07% and nonreassuring fetal status occurring in 0.01% of women. They reported no cases of abruption, cord prolapse, or fetal death.25 Prior studies also have not found an association between transcervical Foley use and chorioamnionitis.26,27 Although women in our study with outpatient ripening had a slightly higher white blood cell count on admission, both remained in the normal range, and the difference in chorioamnionitis was not statistically significant.
We acknowledge several limitations. First, we performed this study at a single academic institution and included only a low-risk patient population. Thus, our inclusion criteria and our institutional practices may not be generalizable to all centers. In addition, our study was unblinded, and it is possible that knowledge of the intervention may have led to the aforementioned differential responses. However, we accounted for an unblinded intervention by using an objective primary outcome of time. We also acknowledge that the outpatient group did not receive concurrent oxytocin at the initiation of cervical ripening (a contraindication) as was done in the inpatient group. Our standard protocol is to use both in the inpatient setting owing to some studies showing that concurrent use results in a shorter time to delivery than sequential use.13,14 Therefore, we would expect a greater difference in time to delivery between groups if we used a sequential approach in the inpatient group. Lastly, we are underpowered for several of our secondary outcomes, and these will need to be evaluated in future studies. Our study had several strengths, including that we performed a randomized controlled trial with adequate allocation concealment and power for the primary outcome.
In conclusion, in nulliparous women undergoing elective induction of labor, outpatient cervical ripening with a transcervical Foley catheter reduced the time from hospital admission to delivery. Larger studies are needed to evaluate cesarean delivery, infection, and other safety outcomes.
Authors' Data Sharing Statement
- Will individual participant data be available (including data dictionaries)? Yes.
- What data in particular will be shared? Upon request, all individual de-identified data will be shared.
- What other documents will be available? Study protocol is available on ClinicalTrials.gov.
- When will data be available (start and end dates)? Beginning immediately and ending 24 months after article publication.
- By what access criteria will data be shared (including with whom, for what types of analyses, and by what mechanism)? Requested data will be shared by the Center for Women's Reproductive Health at the University of Alabama at Birmingham for the purposes of research intended for publication.
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