Efficacy of Oral Isosorbide Mononitrate Sustained-release for Pre-induction Cervical Ripening in Term Pregnant Women in an Outpatient Setting: A randomized controlled trial

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Cheun Chaotrakool
Suppasiri Hayakungchat
Thumwadee Tangsiriwatthana


Objectives: To compare the efficacy of 60 mg oral, sustained-release, isosorbide mononitrate (ISMN SR) with a control for improve pre-induction cervical ripening of term pregnant women in an outpatient setting.
Materials and Methods: In this randomized controlled, superiority trial, 36 women with uncomplicated singleton pregnancy at ≥ 39 weeks gestation and unfavorable cervix attending the antenatal care clinic at Khon Kaen Hospital were randomly assigned to (a) two oral 60 mg doses of ISMN SR every 24 h (n=18) prior to admission for induction of labor or (b) a control group (n=18). The primary outcome was the proportion of favorable cervix on admission. The secondary outcomes were (a) changes in the Bishop score, (b) time from admission to delivery, and (c) neonatal and maternal outcomes.
Results: Demographic characteristics were similar between the groups. The proportion of favorable cervix at 48 h after oral ISMN SR was significantly greater than the control group (0.61 vs 0.17, p = 0.008, RR = 7.85, 95%CI 1.65-37.40). The mean change in the Bishop score was significantly higher in the ISMN SR group than the control (6.05 vs 2.71, p = 0.022). The time from admission to delivery in the ISMN SR was also less than the control (10 vs 23 h, p = 0.002). However, there was no respective significant difference in the rate of cesarean section, maternal complications, or neonatal outcomes.
Conclusion: Our study provides evidence that pre-induction of cervical ripening with 60 mg of oral ISMN SR among outpatient, term pregnant women is effective and with no observed adverse outcomes.


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