Correlation between umbilical vein-to-artery delta pH and type of intrapartum hypoxia in a cohort of acidemic neonates: A retrospective analysis of CTG findings

Introduction: Umbilical artery blood analysis is assumed to give a picture of the acid–base balance of the infant at birth and is considered the gold standard to diagnose neonatal acidemia at birth. The evaluation of umbilical vein pH has been suggested as an adjunct in order to optimize the understanding of the pathophysiology of the hypoxic events in labor. The objective of this study was to assess the correlation between the Delta pH (vein-to-artery) on the umbilical cord and the intrapartum cardiotocography (CTG) patterns in a selected cohort of acidemic neonates. Methods: Retrospective analysis of all CTG traces from non-anomalous term neonates consecutively born with acidemia (pH < 7.05 on the arterial cord) at four European tertiary Maternity Units. Intrapartum CTG traces were collected and their characteristics were reviewed in consensus by three senior Obstetricians. Each case was assigned to one of these four types of intrapartum hypoxia according to the CTG features: acute hypoxia, subacute hypoxia, slowly evolving hypoxia, and chronic hypoxia. The relationship between the different categories of intrapartum hypoxia and the Delta pH on the umbilical cord were evaluated. Results: Overall, 83 acidemic neonates were included. Acute hypoxia, subacute hypoxia, slowly evolving hypoxia, and chronic hypoxia accounted for 19 (22.9%), 24 (28.9%), 24 (28.9%) and 16 (19.3%) cases, respectively. No difference of the Delta pH (p 0.61) was noted across the CTG subclasses, while significantly lower birthweight among cases with chronic hypoxia was found (p 0.03). The mean Delta pH did not vary at comparison between the cases with rapid onset hypoxia (acute + subacute hypoxia) and those with long lasting hypoxia (chronic + slowly evolving) (p 0.59). Conclusions: Within a selected cohort of acidemic neonates, our data do not demonstrate an association between the different CTG patterns of intrapartum hypoxia and the artery-to-vein Delta pH on the umbilical cord.