[Quantitative Cardiotocography--what does it look like and what can we expect]

Area of Science:

• Perinatal Medicine
• Medical Informatics
• Fetal Monitoring

Background:

• Cardiotocography (CTG) is a practical but often unreliable method for fetal surveillance.
• Subjective interpretation of CTG by clinicians limits diagnostic accuracy.
• Objective analysis of fetal heart frequency (FHF) is needed to evaluate diagnostic power.

Purpose of the Study:

• To develop and evaluate a computer-based scoring system for objective fetal heart rate (FHR) analysis.
• To assess the correlation between the FHR score and fetal acid-base balance parameters.
• To identify factors influencing the accuracy of FHR-based fetal surveillance.

Main Methods:

• Fetal heart frequency (FHF) from 583 deliveries was prospectively analyzed using MATLAB.
• A CTG score was developed based on basal FHF, deceleration area, and micro-fluctuation (MF).
• Score cut-off values were determined by correlation with umbilical artery (UA) acid-base parameters, particularly pH.

Main Results:

• The developed score showed significant correlation with UA pH (r = -0.559, P << 10(-4)).
• Micro-fluctuation (MF) and basal FHF were also significantly correlated with fetal acidity.
• Prediction variability for pH was observed, potentially linked to maternal breathing habits.

Conclusions:

• Quantification of FHR variables using a score provides good correlation with fetal acid-base balance.
• The score allows for prediction of actual UA pH within reasonable clinical limits.
• Maternal influence on FHR variability necessitates further investigation, possibly through continuous maternal pCO2 monitoring.