Outcomes
The primary outcome was metabolic acidosis (MA) in cord blood defined as pH < 7.05 and BDecf > 10mmol/L and/or lactate > 10mmol/L (18). If arterial samples were missing, venous samples were used with the same cut-offs as arterial. Since venous pH values are usually less acidotic than arterial, venous levels meeting cut-off criteria for arterial samples are evidently pathological (19).
Secondary outcome measures included alternative combinations of the blood gas parameters, Apgar scores (AS) and various clinical neonatal outcomes: neonatal intensive care unit admission (NICU), neonatal resuscitation interventions, such as continuous positive airway pressure therapy (CPAP), bilevel positive airway pressure (BiPAP) or ventilation. The correlation between scalp blood lactate and umbilical artery blood pH/lactate was determined in relation to the time interval 0-15 minutes, 0-25 minutes, 0-30 minutes and 0-60 minutes from FBS to delivery to define the optimal time-limit for cases to be included in the calculation of the suggested cut-off for intervention.