COMPUTERIZED ANALYSIS OF FETAL HEART-RATE VARIATION IN POSTTERM PREGNANCY - PREDICTION OF INTRAPARTUM FETAL DISTRESS AND FETAL ACIDOSIS

OBJECTIVE: Our purpose was to evaluate whether computerized analysis o f fetal heart rate variation may improve fetal surveillance in postter m pregnancy. STUDY DESIGN: Three hundred thirty-seven pregnant women w ho were delivered after 41 weeks' gestation and who had 610 antenatal tests were included in this study. Fetal tests included a nonstress te st with a computerized analysis of the fetal heart rate, Doppler exami nation of the umbilical artery, and a biophysical profile, performed e very 2 to 4 days. Induction of labor was performed when the fetal hear t rate variation was reduced (<30 msec), when fetal heart rate deceler ations appeared, or when the amniotic fluid index was less than or equ al to 5. The results of the fetal surveillance tests were compared wit h the results of the intrapartum fetal heart rate monitoring and with the metabolic status of the babies at delivery. Sensitivity and specif icity of the various tests in predicting intrapartum fetal distress an d acidosis at delivery were described by means of the receiver-operato r characteristic curve. RESULTS: Ten of 12 fetuses with reduced fetal heart rate variation had a trial of labor. Nine of these 10 fetuses ha d fetal distress during labor. Seven of the 12 fetuses with reduced fe tal heart rate variation were acidotic at delivery (umbilical artery p H <7.2). Overall, there were 10 acidotic fetuses at delivery in the st udy group. Only two of them had an umbilical systolic/diastolic ratio > 95th percentile, three had an amniotic fluid index less than or equa l to 5, and five had fetal heart rate decelerations before labor. Fetu ses who demonstrated an abnormal intrapartum fetal heart rate tracing or who were acidotic at delivery had a significantly higher rate of re duced fetal heart rate variation or decelerations before labor. The la rgest area under the receiver-operator curve curve for predicting feta l acidosis at delivery or fetal distress during labor was achieved by means of computerized analysis of fetal heart rate variation. CONCLUSI ON: A computerized numeric analysis of fetal heart rate variation may improve fetal surveillance in postterm pregnancy.