Abstract
Background:
Cervical priming refers to softening of the cervix and allows uterine contractions to effectively dilate the cervix. Priming agents shorten labor duration and maximize the possibility of vaginal delivery. Prostaglandins work directly on the cervix for priming and indirectly stimulate the myometrium to induce contractions.

Aim:
This study aimed to compare the efficacy of misoprostol and prostaglandin E2 (Dinoprostone gel) as a priming agent before labor induction.

Methods:
A randomized, non-blinded, prospective, interventional study was conducted on 90 women at term pregnancy without any previous uterine scar with a reactive non-stress test (NST) and Bishop score (BS) <6. They received either 50 μg sublingual misoprostol or 0.5 mg of intracervical dinoprostone gel as a priming agent. After 24 hours, women were assessed for progress. Those who did not go into the active phase or were delivered by the priming dose were further induced by 25 mcg of misoprostol 6-hourly for a maximum of six doses. Outcomes measured were change in BSs, number of women delivered in ≤ 24 hours, priming-to-active-phase interval (PAI), maternal and neonatal outcomes. Statistical analysis was performed using chi-square test and t-test.

Results:
The mean change in BS after 24 hours of priming was 5.148 ± 3.047 in the misoprostol and 2.486 ± 2.181 in the dinoprostone group. The mean PAI was 20.93 ± 11.10 and 26.97 ± 11.14 hours in the misoprostol and dinoprostone groups, respectively (p < 0.05). In ≤ 24 hours, 44.44% of women in the misoprostol group were delivered as compared with 17.78% in the dinoprostone gel group (p < 0.05). Mode of delivery and need for oxytocin augmentation were comparable in both groups. There was no significant difference in maternal and neonatal outcomes.

Conclusion:
Sublingual misoprostol (50 μg) is a better cervical priming agent than 0.5 mg intracervical dinoprostone gel in term pregnancy with an unfavorable cervix. Misoprostol reduces PAI with maternal and neonatal outcomes similar to those of dinoprostone gel.

Key words: Bishop score; Induction of labor; Misoprostol; Priming-to-active-phase interval; Prostaglandin E2 (dinoprostone gel).