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32: Umbilical cord arterial lactate compared with pH for predicting neonatal morbidity at term: a prospective cohort study

      Objective

      Recent data suggest a potential role for umbilical arterial lactate as a biochemical measure of neonatal well-being at birth. We tested the hypothesis that umbilical cord arterial lactate is superior to pH for predicting neonatal morbidity at term.

      Study Design

      We conducted a prospective cohort study of all consecutive, non-anomalous, singleton, vertex, term births from 2009-2012. Umbilical arterial lactate and pH were measured immediately after delivery. The primary outcome was a composite neonatal morbidity consisting of neonatal death, intubation, mechanical ventilation, meconium aspiration syndrome, hypoxic encephalopathy, and need for hypothermic therapy. The predictive ability of lactate and pH were compared using receiver-operating characteristics (ROC) curves. Optimal cut-offs of elevated lactate and low pH for predicting the composite neonatal morbidity were estimated based on the maximal Youden index. Sensitivities and specificities were calculated using the optimal cut-offs.

      Results

      Of 4997 subjects meeting inclusion criteria, 4910 had complete lactate, pH and neonatal outcome data for analysis. The composite neonatal morbidity occurred in 56 (1.14%) neonates. Median lactate was nearly 2-fold higher in neonates with the composite neonatal morbidity (5.65 vs 2.90 mmol/L, p<0.001), while median pH values were less distinctly different (7.19 vs 7.29, p<0.001). Lactate was significantly more predictive of neonatal morbidity than pH (ROC curve area: 0.84 vs 0.78, p=0.03) (Figure). The optimal cut-offs for predicting neonatal morbidity were 3.9 mmol/L for lactate and 7.25 for pH. Corresponding sensitivities and specificities were significantly higher for lactate (83.9% and 74.1% vs 75.0% and 70.6%, respectively) (Table).

      Conclusion

      Results of this large prospective cohort study indicate that umbilical cord arterial lactate is a more discriminating measure of neonatal morbidity at term than pH. We propose that lactate replace pH as the measure of neonatal wellbeing at birth.
      Figure thumbnail fx1
      Receiver-operating characteristics curves of lactate levels and pH for prediciting composite neonatal morbidity (N = 4910)
      Tabled 1Umbilical arterial lactate compared with pH for predicting composite neonatal morbidity (N = 4910)
      Figure thumbnail fx2
      CI, confidence interval.