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 isosorbide mononitrate (a nitric oxide donor) on maternal and fetal hemodynamics in pregnant women at term.

STUDY DESIGN

We conducted a randomized controlled trial. Women were randomly selected to receive vaginally administered isosorbide mononitrate, 20 mg (n = 13) or 40 mg (n = 11), or to undergo a vaginal examination 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 resistance index and pulsatility index measurements were performed at 0, 180, and 330 minutes.

RESULTS

Maternal pulse rate was greater after the administration of isosorbide 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-mg and 40-mg isosorbide mononitrate groups than in the vaginal examination-only group (greatest difference in mean systolic and diastolic blood pressure, 15 and 16 mm Hg, respectively; P <.02 and P <.001, respectively). Fetal heart rate was greater in the 40-mg isosorbide mononitrate group than in either the 20-mg isosorbide mononitrate group or the vaginal examination-only group (difference in mean, 15 beats/min; P <.05). No woman required treatment for maternal or fetal tachycardia or maternal hypotension. Neither dose of isosorbide mononitrate had a significant effect on umbilical artery resistance or pulsatility index.

CONCLUSIONS

Vaginal administration of 20 or 40 mg isosorbide mononitrate to pregnant women at term has an effect on both maternal and fetal hemodynamics, but this effect is not clinically significant.