Objective: To compare patterns of uterine activity from low-dose oxytocin begun immediately or six hours after intracervical placement of prostaglandin E2 (PGE2) gel for the induction of labor.
Study design: A total of 50 nonlaboring women at term with an unfavorable cervix (Bishop score < or = 4) were given a 0.5-mg dose of PGE2 gel. Each was then randomized either to be observed or to receive a low dose of oxytocin (2 mU/min, increased by 2 mU/min at 30-minute intervals, as necessary). After the six-hour observation, the patient was reexamined, and a low dose of oxytocin was either begun or continued. An adequate sample size (21 per group) was calculated for evaluating uterine activity changes. Comparisons were made using chi 2 testing, Student's t test and analysis of variance, as appropriate.
Results: There were no differences between the two groups in maternal race, gestational age, predose Bishop score, predose uterine activity or indication for induction. Uterine contractions became more frequent (P < .01) and were judged to be more intense (P < .02) and earlier when oxytocin was used immediately after PGE2 placement. No uterine hyperstimulation or abnormal fetal heart rate pattern was observed that required discontinuation of the oxytocin. The percentages of cases delivering vaginally within 24, 36 and 48 hours were greater when oxytocin was begun immediately in nullipara (P < .01).
Conclusion: Low-dose oxytocin may be started immediately after instilling intracervical PGE2, with shortened time until the onset of adequate contractions.