Propranolol for Induction of Labor in Nulliparas trial a double-blind, randomized, placebo-controlled trial

Propranolol hydrochloride is a nonselective beta-adrenergic antagonist that has a known activity in the myometrium. Small trials have shown that propranolol decreases the duration of induced labor, although those studies are limited by methodological variability.

Our objective was to determine whether the addition of a single dose of propranolol to induce labor in nulliparous women would decrease total time to vaginal delivery.

This study was a double-blind, randomized, placebo-controlled trial of nulliparous patients undergoing term induction of labor with a singleton, nonanomalous gestation. Subjects were randomized to 2 mg of intravenous propranolol hydrochloride or an identical-appearing saline placebo, administered 30 minutes after starting the induction of labor. Investigators, labor floor staff, and patients were blinded to the study drug allocation. The primary outcome was time to vaginal delivery. Secondary outcomes included mode of delivery, duration of the phases of labor, time to full dilation, composite maternal morbidity, and composite neonatal morbidity. Data were analyzed by intention-to-treat analysis with a P value of ≤.05 considered significant.

In this study, 240 patients were enrolled from December 2017 to December 2018, with 121 patients randomized to the propranolol group and 119 to the placebo group. The 2 groups had similar baseline characteristics. Of the patients randomized, 154 (64.2%) delivered vaginally. There was no significant difference in time from the start of the induction of labor to vaginal delivery (13.8±5.4 hours for propranolol vs 14.3±5.3 hours for placebo; P=.58). There was also no difference in the rate of cesarean delivery (38% vs 33.6%; P=.48), time to active labor (11.0±5.0 vs 11.2±4.5 hours; P=.77), or time to full dilation (12.4±5.1 vs 12.8±5.2 hours; P=.60) in patients receiving propranolol compared with those receiving placebo. Subjects randomized to the propranolol group had a significantly lower rate of composite maternal morbidity (28.9% vs 41.2%; risk ratio, 0.70; 95% confidence interval, 0.49-1.00; P=.047). Rates of postpartum hemorrhage (12.4% vs 21.8%; P=.05) and transfusion (0% vs 4.2%; P=.03) were also lower in the treated group. There was no significant difference in neonatal outcomes or composite morbidity (risk ratio, 0.74; 95% confidence interval, 0.44-1.22).

In this study, there is no evidence that the addition of a 1-time dose of propranolol to induce labor in nulliparous women decreases time to delivery or the rate of cesarean delivery. However, propranolol significantly reduced composite maternal morbidity without adverse neonatal effects.