Effects of oxytocin-induced uterine hyperstimulation during labor on fetal oxygen status and fetal heart rate patterns

OBJECTIVE: The objective of the study was to evaluate effects of oxytocin-induced hyperstimulation on fetal oxygen saturation and fetal heart rate patterns. STUDY DESIGN: Uterine activity of 56 women was evaluated retrospectively for hyperstimulation lasting 30 minutes using 2 definitions: group 1: 5 or more but less than 6 contractions in 10 minutes (n = 102, 30-minute periods); group 2: 6 or more contractions in 10 minutes (n = 56, 30-minute periods). Fetal oxygen saturation and heart rate patterns during each period and the preceding 30 minutes of less than 5 contractions in 10 minutes were compared. RESULTS: Hyperstimulation was associated with significant oxygen desaturation: (group 1 = 10.68 [20%] decrease from 52.14 to 41.46; P < .001); group 2 = 15.34 [29%] decrease from 52.02 to 36.68: P < .001) and significantly more nonreassuring fetal heart rate characteristics, compared with normal uterine activity. CONCLUSION: Hyperstimulation is associated with negative effects on fetal status. The more contractions in 30 minutes, the more pronounced the effect.