RESUMEN
Aim of the study: To assess the effects of vaginally administered isosorbide mononitrate [a nitric oxide donor, effox tablets 40 mg] on maternal and fetal hemodynamics and the ripening of the cervix. Study design: We conducted a randomized controlled study: two matched groups were recruited as regards. Parity, bishop score, gestational age. Women that were recruited for induction of labor, were randomly selected to receive vaginally administered isosorbide mononitrate 40 mg [n=40] one tablet [study group]or to undergo vaginal examination only [n=40] [control group]Maternal pulse, blood pressure and fetal heart rate were recorded at 0 base line, every 30 minutes till 6 hours. Umbilical artery resistance index and pulsatility index measurements were performed at 0,3 and after 6 hours. Cervical Bishop scores were measured at 0 base line and at the end of the treatment program period [6 hours from the application of isosorbide mononitrate] Maternal pulse rates were increased after the administration of isosorbide mononitrate, 40 mg, compared to the pulse rates in the vaginal examination only group. [greater difference in means, 16 beets per minute, P<0.01]. Maternal systolic and diastolic blood pressures were decreased in the study group than in the control group [greatest difference in mean systolic and diastolic blood pressure, 15 and 16 mml Hg respectively, with a P<0.001]. Fetal heart rate was increased in the study group, than in the control group, with a difference in mean, 19 beats/minute with a P<0.05. No women required treatment for hypotension or for maternal and fetal tachycardia except for headache, which needs mild analgesics to be relieved. The forty mg dose of isosorbide mononitrate had no significant effect on umbilical artery resistance or pulsatility index. Changes in the Bishop score, was more marked in the 40mg isosorbide mononitrate group than in the control group and the difference was statistically significant P<0.05. Conclusions: Vaginal administration of 40 mg isosorbide mononitrate to pregnant women at term has a safe effect on both maternal and fetal hemodynamics. Thus nitric oxide donors are suitable agents for preinduction cervical ripening at term, and can be used as outpatient method with no need for fetal monitoring, being a uterine relaxing agent