Correlation of fetal scalp blood sampling pH with neonatal outcome umbilical artery pH value.

Purpose: Fetal scalp blood sampling is considered as a complimentary tool in addition to cardiotocography to assess fetal well-being. This blood sampling is important as the obstetrician has to judge and make decisions regarding the further management of the delivery based on this pH result. The aim of this study was to analyze the correlation between fetal scalp blood pH and the umbilical artery pH after birth. Furthermore, it was investigated whether tocolysis, a performed episiotomy or cord encirclement have an influence on the umbilical artery pH.

Methods: This retrospective study over a period of 11 years included all singleton pregnancies without fetal anomalies, which were monitored by fetal scalp blood sampling during labor.

Results: 844 out of 1502 deliveries were included for analysis. The analysis demonstrates a good correlation between fetal scalp pH value and outcome pH value. Subgroup analysis with fetal scalp blood pH <7.20 showed a difference in 40 of 82 cases, with an outcome pH value ≥7.20, but this difference was statistically insignificant. Neither did tocolysis, episiotomy or the presence of cord encirclement show an overall effect, nor did they have an impact on the subgroup.

Conclusion: Obstetricians must consider that the values of fetal scalp blood are not always reliable and can be false. However, on the basis of CTG and fetal scalp blood pH, decisions are made regarding delivery interventions. Therefore, we would encourage the consideration of taking two samples routinely at every attempt of fetal blood sampling.