Benefits of Introducing Universal Umbilical Cord Blood Gas and Lactate Analysis Into an Obstetric Unit

Abstract

Current data suggest that umbilical arterial pH analysis is the most sensitive diagnostic indicator of birth asphyxia. Essential criteria for the diagnosis of birth asphyxia include metabolic acidosis (pH <7.0 and base deficit ≥12 mmol/L) in cord arterial blood. However, it is unclear whether umbilical cord blood gas analysis (UC-BGA) should be performed selectively or at all deliveries. Although many investigators believe that universal use of UC-BGA can improve neonatal outcomes, no studies have evaluated this contention. This observational study investigated the effect of universal UC-BGA at delivery on neonatal outcomes. Between 2003 and 2006, data were obtained for 19,646 live births ≥20 weeks' gestational age at a tertiary level obstetric hospital. Blood gas and lactate analyses were performed on paired umbilical arterial and venous blood samples collected at all deliveries. Interyear UC-BGA differences and the likelihood of metabolic acidosis and other perinatal outcomes were assessed using univariate and multivariate logistic regression analysis, with adjustments for possible confounders. The univariate and adjusted data demonstrated significant improvement in arterial pH, pO2, and pCO2, as well as values for base deficit and lactate levels (P ≤ 0.001 for umbilical blood gas and lactate values). The likelihood of newborns with an arterial pH <7.10 and lactate value >6.1 mmol/L was decreased (adjusted odds ratio [aOR], 0.71; 95% confidence interval [CI], 0.53–0.95 and aOR, 0.37; 95% CI, 0.30–0.46; respectively). Using population-specific fifth and 95th percentiles, a reduction was found in newborns with arterial pH less than the fifth percentile (pH 7.12: aOR, 0.75; 95% CI, 0.59–0.96) and lactate levels more than the 95th percentile (6.7 mmol/L: aOR, 0.37; 95% CI, 0.29–0.49). Reductions were observed both in term (aOR, 0.65; 95% CI, 0.54–0.78) and overall (aOR, 0.75; 95% CI, 0.64–0.87) nursery admissions. Improved perinatal outcomes after universal introduction of UC-BGA were independent of intervention rates. These findings show that introduction of universal UC-BGA is associated with improvements in umbilical artery pH, lactate values, and other perinatal outcomes, which are independent of obstetric intervention.