A randomized comparison of one single dose of vaginal 50 microg misoprostol with 3 mg dinoprostone in pre-induction cervical ripening.

Objective: To compare the efficacy and safety of one single dose of 50 pg misoprostol to one single dose of 3 mg dinoprostone administered vaginally for pre-induction cervical ripening in term-pregnant women, who had indications for induction of labor with unripe cervices.

Study Design: A randomized double-blind controlled trial.

Setting: Bangkok Metropolitan Administration Medical College and Vajira Hospital, Bangkok, Thailand.

Subjects: One hundred and forty-three singleton pregnant women of > or = 37 weeks of gestation, who had indications for termination of pregnancy. All patients had a Bishop score of 0-6, without contraindications for labor induction.

Intervention: The subjects were stratified by parity to nullipara and multipara group. The subjects in each stratum were allocated by randomization to receive a single dose of 50 microg misoprostol or 3 mg dinoprostone, administered vaginally. Twenty-four hours after medication, oxytocin augmentation was given to both groups.

Main Outcome Measure: The Bishop score of cervix at 24 hours after insertion of the studied drugs, the occurrence of abnormal uterine contraction, and the number of vaginal deliveries within 24, 48 hours.

Results: The demographic data and the initial Bishop score (median score 3.5 versus 4.0) were comparable in both groups. The change of score at 24 hours was one unit higher in misoprostol-treated patients compared with dinoprostone-treated patients (mean change score 6.5 versus 5.5, with 95 per cent CI 0.04 to 2.1, p=0.042) but was not of clinical importance. There was a higher frequency of hyperstimulation syndrome in the misoprostol group (6.9% vs 0%) during 8 hours of cervical ripening. Although the difference was not statistically significant (p=0.058), it was clinically important. Comparing vaginal deliveries between the misoprostol and dinoprostone groups, the frequencies of delivery within 24 hours were 46.3 per cent versus 35.7 per cent (p=0.350), and within 48 hours were 88.9 per cent versus 89.3 per cent (p>0.05), non-significantly different. No significant differences were noted between misoprostol and dinoprostone in terms of interval from start of medication to vaginal delivery and neonatal outcomes.

Conclusion: The efficacy of a single 50 microg dose of vaginally administered misoprostol, is not clinically different to 3 mg dinoprostone in cervical ripening. Although the study was not sufficiently large to detect the differences in abnormal uterine contractions between the two groups, there was a higher frequency of hyperstimulation syndrome in the misoprostol group compared to the dinoprostone group. Close utero-fetal monitoring in misoprostol-treated patients is needed.