International Journal of Clinical Obstetrics and Gynaecology

Background: The NOS (Nitric oxide synthase) or the NO system has a regulatory role in the myometrium and cervix during pregnancy and parturition. NOS activity is found to be higher before the onset of labour and decreases during labour thereby having a role in the onset of uterine contractions. Nitric oxide (No) plays an important role in cervical ripening. The aim of this study was to know a better knowledge about the effect of vaginal administration of Isosorbide mono-nitrate on cervical ripening and Induction of labor in term and post term pregnancy.

Materials and Methods: This prospective Observational study is conducted in women with singleton live pregnancy (between 37 to 42 weeks of gestation) and an unfavorable cervix(modified Bishop score of 0-6), requiring induction of labour with different indications in the Department of Obstetrics and Gynaecology at Rajah Muthiah medical college, Chidambaram for a period of 2 years. They are enrolled after assessing inclusion and exclusion criteria. 40mg of Isosorbide mononitrate inserted in the posterior fornix and second dose repeated after 6 hours. Oxytocin was started after 12hours if needed. If bishop score is not changed after 24 hours of insertion, it is considered as induction failure and patient is taken for caesarean section.

Results: There is no association found in age wise distribution. The mean BISHOP score was found to be similar between good contractions and suboptimal contractions at baseline and 6 hours while at 12 hours, the mean of good contractions group was significantly more than that of the Suboptimal contractions group (p<0.05). The mean induction to delivery interval was similar among the participants between good contractions and suboptimal contractions augmentation (p<0.05). Both the groups were similar with regard to maternal side effects and foetal outcome with (p<0.05).

Conclusion: The administration of Isosorbide mononitrate has no effect on the hemodynamic state of the mother and fetus. The use of ISMN by the vaginal route as ripening agent before induction of labor at term helps in improving bishop score and reduces the duration of labor.