Comparing the effect of oral and vaginal isosorbide dinitrate in pre-induction cervical ripening in term pregnancy: A controlled clinical trial

Cervical ripening for labor induction is one of the most important issues in midwifery. Isosorbide dinitrate (ISDN) is one of the most important choices that have been proposed for cervical ripening, but still there are controversies regarding its prescription. The present study aimed to evaluate the effects of vaginal and oral ISDN compared to the control group for pre-induction cervical ripening.

In this non-blinded clinical trial, 149 nulliparous women with term or prolonged pregnancy were randomly selected and divided into three groups by block randomization. The intervention group included vaginal (50 subjects, 40 mg) and oral (49 subjects, 20 mg) ISDN groups. The third group was the control group (50 subjects) which did not receive any medication. The amount of ripening was given by Bishop score evaluated before taking medication and 24 h after taking it.

After 24 h, Bishop score in vaginal ISDN group significantly increased compared to the oral ISDN and control groups (P < 0.001 for both). Although the increase in Bishop score was lower in the oral ISDN group than in the vaginal group, it had a statistically significant increase in comparison to the control group (P = 0.001). All the three groups were matched regarding pregnancy termination and cesarean causes, and there was no statistically significant difference among the three groups (P > 0.05).

Prescribing vaginal ISDN for cervical ripening was effective, and it can be used with confidence.