Labor induction is a common practice in obstetrics with 20% of term pregnancies induced annually, influenced by preinduction cervical ripening. Outpatient cervical ripening is of increasing interest but no preferred agent is used. Isosorbide mononitrate (IMN), a nitric oxide donor is a potential outpatient cervical ripening agent without unwanted side effects noted in several studies. A meta-analysis of 5 randomized controlled trials with 735 participants, comparing the effectiveness and safety of cervical ripening and labor induction by isosorbide mononitrate versus placebo was performed. IntravaginallMN 40mg compared with placebo increased the odds of women to go on labor within 24 hours (OR 2.6) and increased the odds of women to deliver vaginally (OR 1.02). However, IMN also increased the odds of cesarean delivery (OR 1.08) but, indications were not solely attributed to failed induction of labor. There was no significant difference between isosorbide mononitrate and placebo on neonatal outcome and admission. IMN caused hypotension and significantly increased risk of maternal headache but not severe to require treatment. Thus, isosorbide rnononltrate is a feasible outpatient cervical ripening agent that appeared to be effective and safe.