A Randomized Controlled Trial of Propranolol in Nulliparous Patients with Prolonged Labor: Propranolol For Protracted Latent Labor.

Background: Propranolol use has been proposed to shorten the length of labor following prolonged induction.

Objective: We sought to determine if administration of propranolol reduces the duration of labor among nulliparous individuals with prolonged latent labor following induction (IOL) at term.

Methods: An open-label randomized clinical trial was conducted from July 2019 through June 2022 comparing 2mg of intravenous propranolol administration to usual care for prolonged latent labor. Nulliparous individuals undergoing IOL at ≥37 weeks with a singleton gestation and cervical dilation ≤2cm were included. Prolonged latent labor was defined as no cervical change ≥8 hours with ruptured membranes and receiving oxytocin. Labor management was standardized among participants. Our primary outcome was time to delivery.

Results: 80 nulliparous participants (40 propranolol, 40 usual care) were randomized. Propranolol administration did not achieve a significantly faster median time to delivery compared to usual care, (propranolol: 27.7 hrs vs. usual care: 30.4 hrs, p< 0.52). Equal proportions of individuals delivered vaginally within 24hrs of randomization (propranolol: 27.5% vs. usual care: 27.5%, p< 1.0). There was no difference in the cesarean delivery rate between the two groups (57.5% versus 55.0%, p=1.0) and no difference in time to active labor (propranolol: 19.5 hrs vs. usual care: 26.0 hrs, p< 0.22). There were no significant differences in maternal and neonatal outcomes.

Conclusions: Propranolol administration did not shorten the time to delivery or increase vaginal delivery in nulliparous individuals with a prolonged latent labor course. Our findings do not support the use of propranolol for prolonged latent labor in nulliparous patients undergoing IOL at term.