The effect of uterine contractions on intrapartum fetal heart rate analyzed by a computerized system

OBJECTIVE: Our goal was to assess the effect of uterine activity on fetal heart rate indexes during the active phase of labor with a computerized fetal heart rate monitoring system. STUDY DESIGN: Twenty-six healthy women were studied in active labor without analgesia. Fetal heart rate was analyzed by a computerized system (Sonicaid, System 8000), providing a numeric analysis of the fetal heart rate indexes. Montevideo and Alexandria units were used for quantitative assessment of contractions. RESULTS: A significant correlation was found between Montevideo units and short-term variation (r = -0.62, p < 0.001), episodes of high (r = -0.48, p < 0.01) and low (r = 0.58, p < 0.01) fetal heart rate variation, and frequency of large accelerations (r = -0.49, p < 0.01). A significant correlation was also found between Alexandria units and short-term variation (r = -0.645, p < 0.001), episodes of high fetal heart rate variation (r = -0.58, p < 0.01), and frequency of large accelerations (r = -0.49, p < 0.01). CONCLUSIONS: In active labor fetal heart rate variability is significantly affected by the intensity and duration of contractions.