Severe Fetal Acidemia Was Poorly Predicted by the Three-Tiered Fetal Heart Rate Interpretation System [33O

Abstract

INTRODUCTION: The purpose of this study was to evaluate EFM during the hour prior to birth in babies born with an umbilical cord arterial pH <7 for predictors of severe acidemia. METHODS: A retrospective cohort study was performed on babies with umbilical cord arterial pH <7. The last hour of EFM was reviewed. Maternal, neonatal, labor and delivery characteristics were compared using the Chi-squared test for independence and the Fisher's Exact Test. IRB approval was obtained. RESULTS: 30 babies were identified with umbilical cord arterial pH <7. 27%, 73%, and 0% of FHTs during the last hour of EFM of babies with severe acidemia were Category I, II, and III, respectively. 85% and 54% of the severely acidemic babies had moderate variability and accelerations, respectively. Only 8%, 8%, 19%, and 15% of severely acidemic babies had fetal tachycardia, fetal bradycardia, recurrent variable decelerations or recurrent late decelerations, respectively. Delivery was expedited only in the presence of recurrent late decelerations. The presence of a Category I tracing, moderate variability or accelerations was falsely reassuring such that delivery was less likely to be expedited. CONCLUSION: Usage of the three-tiered fetal heart rate interpretation system (Category I, II, and III) was not helpful in identifying babies born with umbilical arterial pH of <7. The majority of FHTs of these severely acidemic babies had moderate variability and accelerations, while less than 20% had fetal tachycardia, fetal bradycardia, recurrent variable decelerations or recurrent late decelerations.