Intrapartum electronic fetal heart rate monitoring and the identification of metabolic acidosis and hypoxic-ischemic encephalopathy.

Objective: The purpose of this study was to determine whether electronic fetal monitoring can identify fetuses with metabolic acidosis and hypoxic-ischemic encephalopathy.

Study Design: The cases were 107 nonanomalous chromosomally normal fetuses with an umbilical arterial pH < 7.0 and base excess < or = 12 mmol/L. Controls were the subsequent delivery that was matched by gestational age and mode of delivery. The last hour of electronic fetal monitoring before delivery was evaluated by 3 obstetricians who were blinded to outcome.

Results: Cases had a significant increase in late and prolonged decelerations/hour and late decelerations/contractions. Those fetuses with hypoxic-ischemic encephalopathy had significant increases in bradycardia, decreased variability, and nonreactivity but no difference in late or variable decelerations/hour. For the identification of hypoxic-ischemic encephalopathy, the sensitivity, specificity, and positive and negative predictive values were 15.4%, 98.9%, 66.7%, and 89.4%, respectively, for bradycardia; 53.8%, 79.8%, 26.9%, and 92.6%, respectively, for decreased variability; 92.3%, 61.7%, 2.7%, and 82.9%, respectively, for nonreactivity; and 7.7%, 98.9%, 50.0%, and 88.6%, respectively, for all 3 abnormalities combined.

Conclusion: Fetal metabolic acidosis and hypoxic-ischemic encephalopathy are associated with significant increases in electronic fetal monitoring abnormalities, but their predictive ability to identify these conditions is low.