iPREFACE Score Predicts Fetal Acidemia in Preterm Labor: An Innovative Method for Predicting Fetal Acidemia Through Fetal Stress Accumulation Assessment [ID 1199]

INTRODUCTION: This study aims to clarify the predictive accuracy of our previously reported iPREFACE score, which was already shown to predict fetal acidemia during full-term labor with high accuracy, in preterm labor. METHODS: We retrospectively analyzed singleton preterm deliveries from April 2017 to January 2024. Exclusion criteria included cases with fetal cardiac malformations, chromosomal abnormalities, insufficient cardiotocography monitoring, cesarean births with decision-to-incision time exceeding 60 minutes, and failure to obtain umbilical cord arterial blood samples. The iPREFACE score was calculated from fetal heart rate waveforms during the last 30 minutes before delivery by summing all levels of the five-tier fetal heart rate waveform classifications, as defined by The Japan Society of Obstetrics and Gynecology, to assess fetal stress accumulation. We determined the cutoff value for fetal acidemia using receiver operating characteristic curve analysis and compared maternal and perinatal outcomes between groups above and below this threshold. RESULTS: Of 5,220 preterm deliveries, 248 met inclusion criteria. The iPREFACE score cutoff for predicting umbilical artery pH less than 7.2 (vaginal deliveries) was set at 22 points, with an area under the curve (vaginal deliveries [all cases]) of 0.85 (0.76). The group with scores of 22 or higher showed a significant trend towards metabolic acidosis in umbilical artery blood gas analysis compared to the group with scores lower than 22. CONCLUSIONS/IMPLICATIONS: The iPREFACE score significantly predicted fetal acidemia in preterm labor. The cutoff value of 22 points was lower than our previously reported 44 points for full-term labor, suggesting the need for heightened attention to decelerations in preterm labor.