Fetal scalp blood sampling: Do pH and lactates provide the same information?

Area of Science:

• Obstetrics and Gynecology
• Fetal Monitoring
• Neonatal Acidosis

Background:

• Fetal blood sampling during labor is crucial for assessing fetal well-being.
• Scalp pH has been the standard for obstetric decision-making, but lactate measurements are also used.
• Discordance between these parameters can impact clinical management.

Purpose of the Study:

• To evaluate the disagreement between fetal scalp pH and lactate levels from the same blood samples during labor.
• To identify factors contributing to discordance in these fetal monitoring parameters.

Main Methods:

• Retrospective analysis of 480 fetal blood samples from 268 singleton pregnancies.
• Correlation assessed using Pearson coefficient; agreement evaluated with Cohen's kappa coefficient.
• Factors influencing discordance analyzed via univariate and multivariable methods.

Main Results:

• Strong correlation (r=-0.83) but only fair agreement (K=0.36) between scalp pH and lactates.
• Discordance observed in 29.4% of samples.
• Meconium-stained fluid, sampling at full dilation, and multiple sampling were associated with discordance.

Conclusions:

• Significant discordance exists between fetal scalp pH and lactate measurements, impacting clinical interpretation.
• Discordance is more prevalent under specific conditions like meconium staining and advanced labor.
• A randomized controlled trial is recommended to compare the clinical utility of pH versus lactate for obstetric decisions.