Labour characteristics and uterine activity: misoprostol compared with oxytocin in women at term with prelabour rupture of the membranes.

OBJECTIVE: To compare the labour pattern and uterine activity of oral misoprostol with oxytocin for labour induction in women presenting with prelabour rupture of membranes at term.

DESIGN: Prospective randomised study.

SETTING: Department of Obstetrics and Gynaecology, Queen Mary Hospital, Hong Kong.

PARTICIPANTS: Eighty women presenting with prelabour rupture of membranes at term.

METHODS: The women were randomised to receive either 100 microg misoprostol orally every 4 hours to a maximum of three doses, or intravenous oxytocin infusion according to the hospital protocol. Intrauterine pressure transducers were inserted one hour before induction of labour in both groups of women. We compared the pattern of uterine activity, the induction-to-delivery interval, duration of labour, mode of delivery and neonatal outcome between the two groups.

RESULTS: Both oxytocin and oral misoprostol caused an increase in uterine activity within one hour of labour induction. Peak uterine activity was reached 6-8 h after oral misoprostol, with persistent effects, and 8-10 h after oxytocin, requiring continuous titration of medication. The duration of labour was significantly reduced in nulliparous women, but not in those who were multiparous in the misoprostol group. The induction-to-delivery interval, the mode of delivery and the perinatal outcome were similar for the two groups.

CONCLUSION: Oral misoprostol caused earlier peak uterine activity, compared with oxytocin (6-8 h vs 8-10 h). Oral misoprostol was not only as effective as oxytocin in inducing labour in women at term with prelabour rupture of the membranes, but it reduced significantly the duration of labour in nulliparous women.