Objective: The effect of parity on labor progression following term pre-labor rupture of membranes (PROM) has been described, but detailed patterns among grand multiparous women remain unclear. Traditional labor models show accelerated labor with increasing parity, yet few studies have specifically examined PROM latency distributions or heterogeneity within high-parity groups. The aim of the present study was to characterize labor progression after term PROM across parity groups, with specific focus on identifying heterogeneity and distinct distributional patterns among grand multiparous women.
Methods: This was a retrospective cohort study including 11 219 women with singleton, cephalic pregnancies at ≥37 weeks gestation who underwent expectant management following term PROM. Women were stratified into three groups: nulliparous (n = 4347), multiparous parity 1-4 (n = 6725), and grand multiparous parity ≥5 (n = 147). The primary outcome was PROM-to-delivery interval analyzed by mean, median, and percentile distribution. Secondary outcomes included mode of delivery and second-stage duration.
Results: Mean PROM-to-delivery interval decreased with increasing parity (nulliparous 13.4 ± 7.1 h vs multiparous 10.4 ± 6.3 h vs grand multiparous 10.2 ± 6.5 h; P < 0.001). While grand multiparous women had labor kinetics comparable to multiparous women at lower percentiles, a biphasic pattern emerged: beyond the 70th percentile, latency in grand multiparous women plateaued and resembled nulliparous progression. Grand multiparous women had the shortest second stage (14.3 ± 9.8 min) and highest spontaneous vaginal delivery rate (96.6%).
Conclusion: Beyond confirming known parity-related differences in labor duration after term PROM, this study demonstrates clinically relevant heterogeneity within the grand multiparous population. A distinct subgroup shows delayed progression that is not captured by mean or median estimates. Distributional, percentile-based assessment may refine counseling and support more individualized timing of intervention following term PROM.
Keywords: grand multiparity; labor progression; parity; pre‐labor rupture of membranes (PROM); vaginal delivery.
© 2026 The Author(s). International Journal of Gynecology & Obstetrics published by John Wiley & Sons Ltd on behalf of International Federation of Gynecology and Obstetrics.