Defining uterine tachysystole: how much is too much?

OBJECTIVE: We sought to determine if uterine tachysystole, >= 6 contractions per 10 minutes, within the first 4 hours of labor induction, is associated with adverse infant outcomes. STUDY DESIGN: This was a prospective cohort study of 584 women >= 37 weeks' gestation undergoing induction of labor with 100 mu g of oral misoprostol. Fetal heart rate tracings were analyzed for contractions per 10 minutes during the initial 4 hours after misoprostol administration. Patients were analyzed based on the maximum number of contractions per 10 minutes. Infant condition at birth was assessed using the fetal vulnerability composite. RESULTS: Adverse infant outcomes showed no association with increasing number of contractions per 10 minutes. Six or more contractions in 10 minutes were significantly associated with fetal heart rate decelerations (P <= .001). Analysis was performed using the maximum number of contractions per 30 minutes with similar results. CONCLUSION: Uterine tachysystole, as currently defined, when occurring remote from delivery is not associated with adverse infant outcomes.