Short term morbidity and types of intrapartum hypoxia in the newborn with metabolic acidaemia: a retrospective cohort study

Objectives: to assess labour characteristics in relation to the occurrence of Composite Adverse neonatal Outcome (CAO) within a cohort of fetuses with metabolic acidaemia. Design: retrospective cohort study. Setting: 3 Italian tertiary maternity units. Population: 431 neonates born with acidaemia ≥36 weeks. Methods: Intrapartum CTG traces were assigned to one of these four types of labour hypoxia: acute, subacute, gradually evolving and chronic hypoxia. The presence of CAO was defined by the occurrence of at least one of the following: Sarnat Score grade ≥2, seizures, hypothermia and death <7 days from birth. Main outcome measures: to compare the type of hypoxia on the intrapartum CTG traces among the acidaemic neonates with and without CAO. Results: The occurrence of a CAO was recorded in 15.1% of neonates. At logistic regression analysis, the duration of the hypoxia was the only parameter associated with CAO in case of acute and subacute pattern (OR 1.3; 95% CI 1.02-1.6 and OR 1.04; 95% CI 1.0-1.1), while the duration of the hypoxic insult and the time from PROM to delivery were both associated with CAO in those with gradually evolving pattern (OR 1.13; 95% CI 1.01-1.3 and OR 1.04; 95% CI 1.0-1.7). The incidence of CAO was higher in fetuses with chronic antepartum hypoxia compared to those showing CTG features of intrapartum hypoxia (64.7 vs. 13.0%; p<0.001). Conclusions: The frequency of CAO seems related to the duration and the type of the hypoxic injury being higher in fetuses showing CTG features of antepartum chronic hypoxia.