Intracervical Foley catheter with and without oxytocin for labor induction with Bishop score ≤3: a secondary analysis

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Background: Combination methods of cervical ripening with Foley and oxytocin has been shown to reduce total time from induction to delivery compared to Foley alone in patients with an unfavorable cervix (Bishop score <6). It is unclear if this is still effective for patients with less favorable cervices as indicated by Bishop score ≤3.

Objective: To determine if inducing labor with Foley catheter and concurrent oxytocin reduces the total time from induction to delivery in subjects with Bishop score ≤3 compared to those receiving Foley catheter alone for cervical ripening.

Study design: This was a secondary analysis of randomized, multicenter trial of patients with a live singleton pregnancy at ≥24 weeks gestation undergoing labor induction with a Foley catheter with a Bishop score <6. This analysis included patients with a Bishop score ≤3. Exclusions included >1 cesarean section, unexplained bleeding, non-reassuring fetal tracing, major fetal anomalies, or other contraindication to vaginal delivery. Subjects were randomized to receive intracervical Foley catheter alone or with concurrent oxytocin infusion. Primary outcome for this analysis was time from induction to delivery. Secondary outcomes included delivery ≤12 hours, time to delivery ≤24 hours, cesarean delivery, total time of oxytocin infusion, need for additional ripening, postpartum hemorrhage, chorioamnionitis, and neonatal intensive care unit (NICU) admission.

Results: A total of 322 patients were enrolled in the primary trial; 151 subjects had an initial Bishop score ≤3 and were included in the secondary analysis (n=77 Foley and oxytocin, n=74 Foley only). Demographics were similar in both groups. Those with a Bishop score ≤3 who received Foley with concurrent oxytocin had a decreased time from induction to delivery compared to patients who received Foley alone for cervical ripening (21.3 vs. 27 hours, p=0.005). The group with Foley and oxytocin administered concurrently also had shorter induction to delivery time when adjusting for BMI, parity status, and first Bishop score (21.5 vs. 26.7 hours, p=0.007). They were more likely to deliver within 24 hours (74% vs. 46%, p=0.001) and not require additional ripening agents (4% vs. 15%, p=0.04). Patients with the Foley alone method were more likely to receive additional ripening method, but had fewer hours of oxytocin infusion (19.1 vs. 12.4 hours, p<.001). There was no difference in the rate of delivery ≤12 hours, cesarean delivery, postpartum hemorrhage, chorioamnionitis, and NICU admission.

Conclusion: Concurrent Foley catheter and oxytocin infusion significantly reduces the time from induction to delivery in patients with Bishop score ≤3 compared to Foley alone, particularly in multiparous patients.

Keywords: dilation; ripening; unfavorable.