Predictive value of electronic fetal monitoring for intrapartum fetal asphyxia with metabolic acidosis

Objective: To determine the predictive value of each fetal heart rate (FHR) variable and of patterns of FHR variables for fetal asphyxia during labor. Methods: This matched case-control study included an asphyxia group of 71 t erm infants with umbilical artery base deficit greater than 16 mmol/L and a control group of 71 term infants with umbilical artery base deficit less t han 8 mmol/L. Each FHR record available for the 4 hours before delivery was scored in 10-minute cycles for each FHR variable. Selected patterns of imp ortant FHR variables were examined during the last hour before delivery for their predictive value for fetal asphyxia. Results: The FHR variables associated with fetal asphyxia included absent a nd minimal baseline variability and late and prolonged decelerations. Fetal heart rate patterns with absent baseline variability were the most specifi c but identified only 17% of the asphyxia group. The sensitivity of this te st increased to 93% with the addition of less specific patterns. The estima ted positive predictive value ranged from 18.1% to 2.6%, and the negative p redictive value ranged from 98.3% to 99.5%. Conclusion: A narrow 1-hour window of FHR patterns including minimal baseli ne variability and late or prolonged decelerations will predict fetal asphy xial exposure before decompensation and newborn morbidity. Thus, with caref ul interpretation, predictive FHR patterns can be a useful screening test f or fetal asphyxia. However, supplementary tests are required to confirm the diagnosis and to identify the large number of false-positive patterns to a void unnecessary intervention. (Obstet Gynecol 1999;93:285-91. (C) 1999 by The American College of Obstetricians and Gynecologists.).