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 of fetal heart rate variation may improve fetal surveillance in postterm pregnancy.

STUDY

DESIGN

Three hundred thirty-seven pregnant women who were delivered after 41 weeks' gestation and who had 610 antenatal tests were included in this study. Fetal tests included a nonstress test with a computerized analysis of the fetal heart rate, Doppler examination of the umbilical artery, and a biophysical profile, performed every 2 to 4 days. Induction of labor was performed when the fetal heart rate variation was reduced (< 30 msec), when fetal heart rate decelerations appeared, or when the amniotic fluid index was < or = 5. The results of the fetal surveillance tests were compared with the results of the intrapartum fetal heart rate monitoring and with the metabolic status of the babies at delivery. Sensitivity and specificity of the various tests in predicting intrapartum fetal distress and acidosis at delivery were described by means of the receiver-operator characteristic curve.

RESULTS

Ten of 12 fetuses with reduced fetal heart rate variation had a trial of labor. Nine of these 10 fetuses had fetal distress during labor. Seven of the 12 fetuses with reduced fetal heart rate variation were acidotic at delivery (umbilical artery pH < 7.2). Overall, there were 10 acidotic fetuses at delivery in the study group. Only two of them had an umbilical systolic/diastolic ratio > 95th percentile, three had an amniotic fluid index < or = 5, and five had fetal heart rate decelerations before labor. Fetuses who demonstrated an abnormal intrapartum fetal heart rate tracing or who were acidotic at delivery had a significantly higher rate of reduced fetal heart rate variation or decelerations before labor. The largest area under the receiver-operator curve curve for predicting fetal acidosis at delivery or fetal distress during labor was achieved by means of computerized analysis of fetal heart rate variation.

CONCLUSION

A computerized numeric analysis of fetal heart rate variation may improve fetal surveillance in postterm pregnancy.