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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.

Although electronic fetal heart rate monitoring remains the most popular technique for fetal surveillance during labour, there is much concern about the ever rising Caesarean section rate, probably partly due to this practice. Fetal blood sampling is still the gold standard when it comes to measuring fetal oxygenation. There is enough evidence that the combination of EFM and FBS is more efficient in detecting fetal hypoxia and prevents an unnecessary high intervention rate. Another toot to assess the efficacy of intrapartum fetal monitoring is the measurement of pH and blood gases in the umbilical cord blood. This method can also rule out fetal hypoxia in cases with unreassuring fetal heart rate patterns, meconium and low Apgar scores. Continuing inadequate fetal oxygenation during labour may lead to pathological fetal acidaemia. This means that there is a mixed acidosis in the fetal blood with hypercarbia and a substantial base deficit. A pH