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. (Am J Obstet Gynecol 1998;178:436-40.)