pH, base deficit or lactate. Which is better for predicting neonatal morbidity?

Objective: To determine which parameter of the umbilical arterial cord gas analysis, pH, base deficit (BD) or lactate has a bigger predictive ability for neonatal morbidity at term.

Method: We conducted a four-year retrospective cohort study including all non-anomalous, singleton, vertex, term births with neonatal acidemia (umbilical arterial cord gas pH ≤ 7.1). The primary outcomes were a composite neurological morbidity and a composite systemic morbidity. The predictive ability of lactate, BD and pH was compared using receiver operator characteristic (ROC) curves. Optimal cutoff values of lactate, BD and pH were estimated based on their maximal Youden Index.

Results: We identified 466 acidemic neonates who had paired and validated cord blood gas data. The ROC curve analysis revealed that pH, BD and lactate had a similar predictive ability for neurological (AUC: 0.81; 0.78; 0.83, respectively) and systemic neonatal morbidity (AUC: 0.77; 0.82; 0.82, respectively). The combination of pH ≤ 7.0 and lactate ≥ 7.0 mmol/L presented similar validity to that of pH ≤ 7.0 and BD ≥ 12 mmol/L, but both were comparable to pH alone.

Conclusions: pH, BD and lactate have similar predictive ability for adverse neonatal outcomes among acidemic neonates. Umbilical arterial lactate could replace BD as a measure of the metabolic component in acidemic neonates. However, neither BD nor lactate demonstrated in this study to improve the predictive ability of pH alone for short-term neonatal outcomes.