Interrelations among abnormal cardiotocograms in labor, arterial cord blood pH, base deficit and apgar scores in pregnancies

Abstract

Objective: Our purpose was to evaluate the clinical validity of electronic heart rate monitoring in pregnancies and to predict fetal acidosis. Materials and Methods: Fifty-five women between 38 and 40 weeks''gestational age who had electronic fetal monitoring were recruited prospectively and umbilical artery cord gas analysis was performed at delivery. One investigator, blinded to the cord blood gases outcome and using the standard guidelines for fetal heart rate monitoring reviewed all tracings with decreased variability (amplitude -14 mmol/L were interpreted as fetal acidosis. Results: The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of abnormal tracings for predicting low Apgar scores were 100 %, 90.2 %, 44.4 %, and 100 °/o for 1-minute, and 100 %, 88.9 %, 14.3 %, and 100 %, for 5-minute, respectively. The sensitivity, specificity, PPV and NPV of abnormal tracings for predicting umbilical arterial pH of 7.1 were 88.8 %, 97.8 %, 88.9 %, and 97.8 %, respectively. The sensitivity, specificity, PPV and NPV of abnormal tracings for predicting base deficit were 75.0 %, 93.6 %, 66.7 %, and 95.6 %, respectively. Conclusion: Intrapartum fetal heart rate monitoring is useful to detect fetal acidemia, nevertheless, the operative delivery rate is higher among patients with abnormal fetal heart rate patterns. The obstetrician should therefore, be aware of the high false positivity rate of abnormal tracings in order to avoid unnecessary cesarean delivery.