We evaluated the predictive association between umbilical arterial blood gas parameters (pH and base deficit) and subsequent hypoxic-ischemic encephalopathy severity in term neonates with 5-minute Apgar scores ≤5.

Hypoxic-ischemic encephalopathy (HIE) severity following perinatal

asphyxia is graded by clinical criteria (Sarnat stages I–III) and strongly influences

outcomes. Umbilical arterial blood gases, including pH and base deficit (BD), reflect the

degree of foetal acidemia from intrapartum hypoxia. We evaluated whether umbilical

arterial pH and BD at birth predict the subsequent stage of HIE in term neonates with 5-

minute Apgar scores ≤5.

In this prospective cohort of term neonates (gestational age ≥37 weeks) with 5-minute Apgar scores ≤5, we recorded umbilical arterial blood pH and BD at birth (double-clamped cord samples). Neonates were examined and classified according to the Sarnat criteria. We compared mean pH and BD across HIE groups (ANOVA) and assessed correlations between the two.

Eighty infants met the inclusion criteria. By Sarnat staging, 40 infants (50%) had no encephalopathy, 20 (25%) had HIE I, 17 (21.25%) had HIE II, and 13 (16.25%) had HIE III. Mean pH differed significantly among the groups and decreased with increasing HIE severity (ANOVA p<0.001). Mean base deficit likewise increased. Both pH and BD showed strong monotonic relationships with the HIE stage. Spearman’s correlation of pH with HIE severity was ρ = -0.94 (p<0.001), indicating that lower pH (more acidemia) was associated with higher HIE stages. Base deficit showed ρ = +0.80 (p < 0.001) with HIE stage, indicating greater BD (more severe metabolic acidosis) in more severe HIE.

In terms of neonates with low 5-minute Apgar scores, more severe cord arterial

acidemia (lower pH, higher BD) was strongly associated with more severe HIE. These

findings support the clinical value of umbilical cord blood gas analysis in newborns at

high risk for asphyxia.