Vaginal application of the nitric oxide donor isosorbide mononitrate for preinduction cervical ripening: A randomized controlled trial to determine effects on maternal and fetal hemodynamics

OBJECTIVE: Our aim was to assess the effects of vaginally administered isos orbide mononitrate (a nitricoxide donor) on maternal and fetal hemodynamics in pregnant women at term. STUDY DESIGN: We conducted a randomized controlled trial. Women were random ly selected to receive vaginally administered isosorbide mononitrate, 20 mg (n = 13) or 40 mg (n = 11), or to undergo a vaginal ex amination only (n = 12). Maternal pulse, blood pressure, and fetal heart rate were recorded at baseline and then every 30 minutes until 360 minutes. Umbilical artery res istance index and pulsatility index measurements were performed at 0, 180, and 330 minutes. RESULTS: Maternal pulse rate was greater after the administration of isosor bide mononitrate, 20 or 40 mg, compared with the pulse rate in the vaginal examination-only group (greatest difference in means, 21 beats/min; P < .01 ). Maternal systolic and diastolic blood pressures were greater in the 20-m g and 40-mg isosorbide mononitrate groups than in the vaginal examination-o nly group (greatest difference in mean systolic and diastolic blood pressur e, 15 and 16 mm Hg, respectively; P < :02 and P < .001, respectively). Feta l heart rate was greater in the 40-mg isosorbide mononitrate group than in either the 20-mg isosorbide mononitrate group or the vaginal examination-on ly group (difference in mean, 15 beats/min; P < .05). No woman required tre atment for maternal or fetal tachycardia or maternal hypotension. Neither d ose of isosorbide mononitrate had a significant effect on umbilical artery resistance or puisatility index. CONCLUSIONS: Vaginal administration of 20 or 40 mg isosorbide mononitrate t o pregnant women at term has an effect on both maternal and fetal hemodynam ics, but this effect is not clinically significant.