Aim: To compare the efficacy of glyceryl trinitrate (GTN), dinoprostone and misoprostol for preinduction cervical ripening in primigravida at term.
Methods: Sixty-five term primigravida, each with an unfavorable cervix (Bishop score </=5), were randomized to receive GTN (0.5 mg perivaginally, n = 21), dinoprostone gel (0.5 mg intracervically, n = 21) and misoprostol (50 microg perivaginally, n = 23) for a maximum of two doses, 6 h apart. Statistical analysis included paired t-tests to compare pre- and post-treatment Bishop scores, one-way analysis of variance (anova) tests to compare quantitative variables and chi-squared tests to compare the proportion of subjects achieving favorable Bishop scores.
Results: Baseline Bishop scores were similar in the GTN (3.4 +/- 0.9), dinoprostone (3.4 +/- 1.0) and misoprostol groups (3.2 +/- 1.2). The final outcome was favorable (Bishop score >6) in a greater proportion of subjects in the misoprostol (n = 18, 81.8%) and dinoprostone (n = 14, 66.7%) groups compared with the GTN group (n = 11, 55%). In subjects with a severely unfavorable cervix (Bishop score </=3), treatment with misoprostol led to a favorable response in 61.6% of patients compared with 45.6% in the misoprostol group and 33.3% in the GTN group. A significant improvement was noted in the Bishop score of all three groups (P < 0.001) but the increase in Bishop score was greater in misoprostol (3.5 +/- 2.1) and dinoprostone groups (2.8 +/- 1.5), compared with the GTN group (2.0 +/- 1.0, ANOVA F = 4.8, P = 0.01). Hyperstimulation and tachysystole were observed only in the misoprostol (9% and 4.3%) and dinoprostone groups (4.7% and 16.2%). The most common adverse effect in the GTN group was headache, which was observed in 47.6% of this group's subjects.
Conclusion: The findings of the present study suggest that GTN is safer, but less efficacious, compared with prostaglandins for preinduction cervical ripening at term.