Objective: The objective of this study was to determine if the discriminatory intrapartum amniotic fluid index can reliably predict respiratory or metabolic acidosis in the newborn.
Study design: Among 256 parturients at 37 weeks' gestation or more, the intrapartum amniotic fluid index was obtained in early labor, and umbilical arterial blood gas analysis was performed within 30 minutes of delivery. The mean (+/- SD) amniotic fluid indices in labor among newborns with no acidosis versus those with respiratory or metabolic acidosis were compared. A receiver operating characteristic curve was used to determine the best discriminatory intrapartum amniotic fluid index for respiratory and metabolic acidosis.
Results: Statistical analysis revealed that the mean intrapartum amniotic fluid index among 12 newborns with respiratory acidosis and 26 with metabolic acidosis was significantly lower than the mean index in 218 newborns without fetal acidemia. Despite the differences in the mean intrapartum amniotic fluid index in the three groups analyzed, the receiver operating characteristic curve indicated that an intrapartum amniotic fluid index alone is a poor test for predicting acidosis (respiratory or metabolic) in the neonate.
Conclusion: The mean intrapartum amniotic fluid index in labor among newborns with respiratory or metabolic acidosis was significantly lower than that among nonacidotic newborns. The receiver operating characteristic curve indicated that the intrapartum amniotic fluid index cannot reliably distinguish nonacidotic infants from those with respiratory or metabolic acidosis.