A masked randomized comparison of oral and vaginal administration of misoprostol for labour induction

Bennett, Kelly Angela (2000) A masked randomized comparison of oral and vaginal administration of misoprostol for labour induction. Masters thesis, Memorial University of Newfoundland.

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Abstract

Objective: To test the null hypothesis that administering misoprostol orally or vaginally will result in no difference in time to vaginal birth, and to determine whether different frequencies of tachysystole and hyperstimulation are associated with route of administration. -- Methods: Two hundred six women after 37 completed weeks' gestation who presented with an indication for induction were randomly assigned to receive misoprostol (50 μg) orally or vaginally every 4 hours as needed to induce labour. Placebo use and allocation concealment accomplished blinding until data analysis was completed. Sample size was calculated to allow a two tailed α of .05 and power (1-β) of 80%. All fetal heart rate and uterine activity graphs were classified according to Curtis' criteria before the induction groups were unmasked. -- Results: Analysis involved 104 women in the oral group and 102 in the vaginal group. The mean time (± standard deviation) to vaginal birth with oral misoprostol was 1072 (±593) minutes compared with 846 (±385) minutes with the vaginal protocol (P = .004). There were no significant differences in cesarean rate, epidural use or neonatal outcomes. More frequent tachysystole for 20 minutes (P < .01) and hyperstimulation (P < .04) were observed with vaginal misoprostol. No neonatal asphyxia occurred in either group. -- Conclusion: Misoprostol effectively induces labour, given orally or vaginally. There is a shorter interval to vaginal birth with vaginal application; however, the more frequent occurrence of fetal heart graph abnormalities in this group suggests that, until the optimal dosing interval for vaginal use is determined, the preferred route of misoprostol administration might be oral.

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