Excessive uterine activity accompanying induced labor

Objective: To estimate the incidence and timing of excessive uterine activi ty accompanying induction of labor with misoprostol using different routes (oral or vaginal) and forms (intact tablet or crushed) and to compare these with dinoprostone gel, oxytocin, and spontaneous labor. Methods: This retrospective cohort study included 519 women at term who had labor induced and 86 women at term in spontaneous labor. Induction agents included misoprostol, dinoprostone, or oxytocin. Fetal heart rate and uteri ne activity tracings were analyzed independently by three maternal-fetal me dicine physicians. The diagnosis of tachysystole or hyperstimulation requir ed the agreement of two or more reviewers. Results: The incidence of tachysystole was highest with misoprostol adminis tered by vaginal tablet (misoprostol vaginal tablet 50 mug every 4 hours, 4 8.6%; vaginal tablet crushed 50 mug and suspended in hydroxyethyl gel every 4 hours, 30.7%, P = .009; oral tablet 50 mug every 4 hours, 22.2%, P = .00 1; oral tablet crushed 50 mug every 4 hours, 15.5%, P < .001; dinoprostone gel, 33.0%, P = .022; intravenous oxytocin, 30.2%, P = .027; and spontaneou s onset of labor, 23.3%, P < .001). Hyperstimulation occurred more often wi th dinoprostone gel (16.5%) than with other forms of induction or spontaneo us labor. Hyperstimulation occurred significantly more often with vaginal m isoprostol crushed tablet (7.9%) and vaginal misoprostol intact tablet (7.6 %) than with crushed oral misoprostol (1.0%) (P = .016 and .018, respective ly). There was a shorter time to tachysystole with increasing doses of vagi nal misoprostol tablet (P = .01). Conclusion: The incidence of tachysystole and hyperstimulation, and time to tachysystole, varied depending on the route and form of misoprostol given. (Obstet Gynecol 2001;97:926-31. (C) 2001 by The American College of Obstet ricians and Gynecologists.).