Objective: To conduct a systematic review and meta-analysis of all randomized controlled trials (RCTs) that evaluated the efficacy and safety of isosorbide mononitrate (IMN) in promoting cervical ripening during labour induction.
Methods: Six major databases were searched from inception until 22 April 2021. The risk of bias of included studies was assessed. Various endpoints (n = 21) were meta-analysed, and the endpoints were pooled as mean differences (MD) or risk ratios (RR) with 95% confidence intervals (CI).
Results: In total, 23 RCTs were included in this review, comprising 26 intervention arms and a total of 4305 patients (2210 and 2095 patients were allocated to the IMN and control groups, respectively). Pertaining to obstetric-related maternal outcomes, the pooled analysis showed that admission to delivery time and rate of caesarean delivery were significantly reduced in the IMN group. Moreover, the mean Bishop score and the mean change in Bishop score were significantly increased in the IMN group. Pertaining to drug-related maternal side effect outcomes, the pooled analysis showed that the rates of headache, palpitations, nausea and flushing were significantly lower in the IMN group. Pertaining to neonatal outcomes, the pooled analysis showed no significant difference between the two groups in terms of the rates of neonatal intensive care unit admission, neonatal death, fetal distress, meconium-stained water, Apgar score < 7 at 1 and 5 min, and mean Apgar score at 1 and 5 min.
Conclusion: IMN correlated with several obstetric-related maternal outcomes. IMN was not associated with adverse neonatal outcomes, but was associated with substantial drug-related maternal side effects.
Keywords: Cervical ripening; Isosorbide mononitrate; Labour induction; Nitric oxide; Pregnancy.
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