Efficacy of Propranolol to Reduce Cesarean in Prolonged Labor: a Double-Blind Multi-Site Placebo-Controlled Randomized Trial

Biologic plausibility and prior small studies suggest that propranolol may decrease the likelihood of cesarean delivery (CD) among patients with prolonged labor, but prior trials have been heterogenous and conflicting. This trial compared CD rates in patients with prolonged labor randomized to IV propranolol vs. placebo We conducted a double-blind placebo-controlled randomized trial at two hospitals in a large academic health system. Eligible patients were ≥36 weeks with a singleton gestation and prolonged labor, defined as ruptured membranes and receiving oxytocin with 1) dilation < 6 cm after ≥8 hours or 2) dilation ≥6 cm and < 1 cm change over ≥2 hours. Patients with severe preeclampsia, maternal heart rate < 70 bpm, asthma, diabetes on insulin, or a cardiac contraindication to β blockade were excluded. The primary outcome of CD risk was compared between patients randomized to propranolol (2mg IV) vs. placebo (2mL normal saline IV). Secondary outcomes included labor length and maternal and neonatal morbidity. A total sample size of 328 was required to see a 15% absolute reduction in CD with a baseline rate of 45% and 80% power; however, the trial was stopped for futility during an interim analysis From July 2020-June 2022, 349 patients were eligible and approached; 164 were enrolled and randomized: 84 propranolol; 80 placebo. There were no differences in demographics between groups (Table 1). 60% of the population was Black, 84% were nulliparous and the median BMI was 29.2 kg/m2. The risk of CD was not different between groups (57% propranolol vs. 57% placebo, p=1.0). There was a higher risk of maternal morbidity comparing propranolol to placebo (12% vs. 6%, p=0.21), driven mostly by blood transfusion (10% vs. 2%, p=0.099), although this was not statistically significant In this multi-site, double-blind, placebo-controlled randomized trial, propranolol was not effective in reducing the risk of CD compared to placebo in patients with prolonged labor. This medication confers no benefit for the management of prolonged labor and may be associated with potential risk.View Large Image Figure ViewerDownload Hi-res image Download (PPT)