Outpatient cervical ripening with nitric oxide donor isosorbide mononitrate prior to induction of labor

Objective: To examine the effectiveness and safety of outpatient vaginal administration of isosorbide mononitrate (IMN) to induce cervical ripening. Methods: A prospective, double-blind, placebo-controlled, randomized clinical trial was conducted on 102 singleton term pregnant women with unfavorable cervices who were randomly assigned to receive outpatient intravaginal IMN or placebo before admission for induction of labor. The main outcome variable was time from hospital admission to delivery. Secondary outcomes included fetal and maternal morbidity, labor characteristics, and incidence of cesarean delivery. Results: The admission–delivery interval was 13.45 ± 6.63 and 20.12 ± 8.19 h (P = 0.0001) for the IMN and placebo groups, respectively. Of the IMN patients 62.75% needed prostaglandins for cervical ripening versus 90.2% with placebo (P = 0.002). The incidence of tachysystole was significantly lower in the IMN group (P < 0.05) but there were no significant differences in cesarean delivery rate, neonatal outcomes, and incidence of hyperstimulation. Conclusions: Outpatient use of IMN resulted in shorter admission to delivery interval, and was associated with less prostaglandin use and lower incidence of uterine tachysystole.