Aims. Prostaglandin E2 is the most commonly used drug for cervical ripening prior to labour induction. However, there are concerns regarding uterine tachysystole and nonreassuring fetal heart (N-RFH). Isosorbide mononitrate (IMN) has been used successfully for cervical ripening. The present study was conducted to compare the two drugs for cervical ripening at term in hospital. Methods. Two hundred women with term pregnancies referred for induction of labour with Bishop score less than 6 were randomly allocated to receive either 40？mg IMN tablet vaginally ( ) or 0.5？mg PGE2 gel intracervically ( ). Adverse effects, progress, and outcomes of labour were assessed. Results. PGE2 group had significantly higher postripening mean Bishop score, shorter time from start of medication to vaginal delivery (13.37 ± 10.67 hours versus 30.78 ± 17.29 hours), and shorter labour-delivery interval compared to IMN group (4.53 ± 3.97 hours versus 7.34 ± 5.51 hours). However, PGE2 group also had significantly higher incidence of uterine tachysystole (15%) and N-RFH (11%) compared to none in IMN group, as well as higher caesarean section rate (27% versus 17%). Conclusions. Cervical ripening with IMN was less effective than PGE2 but resulted in fewer adverse effects and was safer especially in high risk pregnancies. 1. Introduction Labour induction in unfavourable cervix is tedious and prolonged resulting in high incidence of failed induction and hence operative deliveries. Therefore, prostaglandin E2 (PGE2, dinoprostone gel) and PGE1 (misoprostol) are commonly used for success of labour induction and to reduce rate of caesarean section [1]. Prostaglandins are quite effective for cervical ripening [2] but have a high incidence of hyperstimulation and tachysystole which may compromise the fetus [3, 4]. An ideal cervical ripening agent should ripen cervix without stimulating uterine activity. Nitric oxide (NO) donors such as isosorbide mononitrate (IMN) and glyceryl trinitrate (GTN) effectively induce cervical ripening without causing uterine contractions by rearranging cervical collagen and ground substance which softens the cervix [5–8]. The efficacy and safety of NO donors have been established in various studies [9–12] but there has been no Indian study to compare IMN with PGE2 gel for preinduction cervical ripening in term high risk pregnancies. With this background in mind, the present study was planned to compare the efficacy and safety of IMN with PGE2 gel for cervical ripening in term pregnancy in Indian population. 2. Methods A prospective, randomized study was
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