(741) Total deceleration area as a predictor of neonatal acidemia in vacuum extraction deliveries

Total deceleration area is known to have the greatest predictive ability for neonatal acidemia and its measure might help in estimating intrapartum fetal acid-base status. We aimed to investigate the correlation between total area under the curve of decelerations (dAUC) and neonatal acidemia in vacuum extractions (VE).

Study Design: This was a retrospective cohort study in a tertiary medical center. We included only VE performed due to non-reassuring fetal heart rate (NRFHR). Electronic fetal monitoring (ECM) in the 120 minutes preceding the delivery were interpreted by two obstetricians that were blinded to the fetal outcomes. Total dAUC was calculated as the sum of AUC for each deceleration, Units = (heartrate change in BPM*time in seconds)/2. Mean total dAUC was calculated using the 2 measurements for each ECM. In cases of high inter observer variability between measurements ( >30% difference in dAUC), a third measurement was performed by a senior obstetrician and was used for the analysis.

Results:

Included for analysis 85 VE. Mean dAUC was 42,908 units + 17,940, mean umbilical cord pH was 7.19 + 0.14. Multivariable linear regression, adjusted for gestational age, nulliparity, diabetes mellitus and fetal weight, revealed a negative correlation between dAUC in the 60 minutes preceding delivery and umbilical cord pH. For every 10K units increase in dAUC, the cord pH decreased by 0.02 (p=0.049, 95%CI -0.05-0.00). Kiwi Omni-cup was associated with an increase in umbilical cord pH (an 0.082 increase in pH as compared to Ventouse-Mityvac cup; p=0.039, 95%CI -0.00-0.16). End stage bradycardia/tachycardia and decreased variability in the 30 minutes preceding delivery were not correlated with a change in umbilical cord pH.

Conclusion: A correlation was demonstrated between dAUC in the 60 minutes preceding delivery and umbilical cord pH. Using dAUC might have value as a predictor of neonatal acidemia despite expediting the delivery by VE.