Misoprostol versus low-dose oxytocin for cervical ripening: a prospective, randomized, double-masked trial.

Objective: A variety of cervical ripening agents exist, yet none is ideal. We performed a prospective, randomized, double-masked comparison of low-dose minimal-escalation oxytocin to misoprostol in a predominantly high-risk population.

Study Design: Patients were allocated prospectively in a double-masked, randomized, stratified basis by an investigational pharmacist between December 1996 and December 2000 to receive either active intravenous oxytocin and placebo intravaginal misoprostol or intravenous placebo oxytocin and 50 microg of active intravaginal misoprostol. The infusion rate of oxytocin was increased from 1 to 4 mU/min; misoprostol (25 microg) was repeated at 4 hourly intervals if there were <3 uterine contractions per 10-minute interval.

Results: Demographic characteristics did not differ between study groups nor did the indications for induction. Overall, the interval to delivery was less in the misoprostol group; however, vaginal delivery occurred in 61% versus 66% (not significant) of patients in the misoprostol versus oxytocin group. Indication for cesarean delivery in the misoprostol group was fetal intolerance to labor in 27% compared with 8% in the oxytocin groups (P <.05), whereas labor abnormalities were more commonly the cause in the oxytocin group versus misoprostol (26% vs 10%, P <.05). The proportion of patients was similar in each group overall and when evaluated on the basis of parity and when delivery was compared at 12, 24, and 36 hours after the initiation of cervical priming.

Conclusion: Our data indicate that misoprostol and low-dose minimal-escalation oxytocin appear to be equally effective for cervical priming. Low-dose oxytocin may have a preferential role in the high-risk parturient whose fetus is at increased risk for fetal intolerance to labor