Comparison of Isosorbide Mononitrate Versus Misoprostol in Cervical Ripening at Term Before Induction of Labor: A Clinical Trial

[Objectives]The aim of this study was to compare the effect of nitric oxide (Isosorbide mononitrate) versus misoprostol in cervix ripening and labor progression.[Methods]This study was a clinical trial. One hundred females with term pregnancies, referred for induction of labor with bishop score of six or less, were randomly allocated to receive either 40 mg Isosorbide Mononitrate (IMN) tablet vaginally or 25 µg misoprostol vaginally every six hours for a maximum of three doses. P value of less than 0.05 was considered statistically significant.[Results]The bishop score decreased significantly due to increasing abortion numbers (P = 0.04; r = -0.19), yet this relationship in the two studied groups wasn’t significant (P misoprostol = 0.67; r = -0.06, and PIMN = 0.57; r = -0.05). The mean primary bishop score was similar in the two groups (P = 0.06) yet the final score in the IMN group was significantly lower than the misoprostol group (P = 0.001). Also, Apgar score in the IMN group was significantly higher than the misoprostol group (P = 0.02). There was a significant difference between the side effects (meconium amniotic fluid, nausea, atony, abdominal pain and tachysystole) and medication group, while this was significantly lower in IMN than the misoprostol group (P = 0.001). P values of less than 0.05 were considered statistically significant.[Conclusions]Cervical ripening with IMN resulted in fewer adverse effects, and it was safer to use for cervical ripening. Therefore, it could be a good substitute for patients with a contraindication for misoprostol.