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.