Safety and Efficacy of Sequential Labor Induction Methods After Failed Primary Induction of Labor: A Retrospective Cohort Study.

BACKGROUND: Induction of labor (IOL) is a common obstetric intervention; however, management following failed primary induction remains clinically challenging. Sequential use of pharmacological and mechanical induction methods is practiced in many institutions, although evidence supporting this approach remains limited. OBJECTIVE: To evaluate the safety and effectiveness of sequential induction strategies using prostaglandin E2 (PGE2) gel, dinoprostone vaginal pessary (Propess), and intracervical Foley catheter following failed primary induction. MATERIALS AND METHODS: This retrospective cohort study was conducted at Ibri Regional Hospital in Oman between January 2023 and December 2025. Women with singleton cephalic pregnancies at ≥37 weeks' gestation who failed an initial induction course and subsequently underwent sequential induction were included. Participants were categorized into six groups (A-F) according to the induction sequence used. Group F (n = 1) was included in the overall cohort but was reported descriptively and excluded from inferential analyses because of the single-case limitation. The primary outcome was vaginal delivery. Secondary outcomes included achievement of active labor, induction-to-delivery interval, mode of delivery, maternal complications, and neonatal outcomes. Statistical analyses were performed using IBM SPSS Statistics version 29.0 (IBM Corp., Armonk, New York, USA). The Kruskal-Wallis test and chi-square test were used for group comparisons, with p < 0.05 considered statistically significant. RESULTS: A total of 145 women underwent sequential induction. Among groups A-E, 125 women (86.8%) achieved active labor, and 96 (66.7%) had a spontaneous vaginal delivery. Rates of progression to active labor did not differ significantly among groups A-E (p = 0.353). Among women who achieved active labor, vaginal delivery rates differed significantly according to the induction sequence used (p < 0.001), with the highest rate observed in the repeated PGE2 gel group. However, this group also had a significantly higher parity. The induction-to-delivery interval differed significantly between groups (p < 0.001), with shorter intervals observed among women receiving prostaglandin followed by an intracervical Foley catheter. Serious maternal complications were uncommon, and no cases of uterine rupture or placental abruption were recorded. Neonatal outcomes, including Apgar scores and neonatal intensive care unit (NICU) admissions, were comparable across groups. CONCLUSION: Sequential induction following failed primary IOL was associated with acceptable maternal and neonatal outcomes in the study cohort, and the strategies involving dinoprostone formulations may be associated with a reduced likelihood of cesarean delivery in selected patients. Prospective studies with standardized protocols and multivariable adjustment are required to determine the optimal sequencing strategy.