[A new approach to quantitative electronic foetal heart-rate analysis]

Area of Science:

• Perinatology
• Fetal Monitoring
• Neonatal Acid-Base Balance

Background:

• Established correlation between fetal heart rate (FHR) and acid-base balance (ABB) offers diagnostic potential.
• Current FHR analysis methods (scoring procedures) are discontinuous and computationally intensive.
• Need for a continuous, less complex FHR evaluation method for improved diagnostic accuracy.

Purpose of the Study:

• To develop and validate a continuous FHR analysis method for assessing fetal acid-base balance.
• To introduce the WAS index as a novel tool for real-time FHR parameter evaluation.
• To correlate the WAS index with fetal acid-base balance parameters for prognostic accuracy.

Main Methods:

• Analysis of 465 direct FHR recordings (last 30 minutes) using custom MATLAB programs.
• Computation of five FHR variables per minute, including microfluctuation, oscillation amplitude, and mean frequency.
• Development of the WAS index based on FHR characteristics in awake, acidotic, and sleeping states; computation of WAS score and prognostic pH.

Main Results:

• Oscillation amplitude and microfluctuation showed the closest correlation with actual pH, UA under hypoxic/acidotic conditions.
• The WAS score, computed from the last 30 minutes of FHR tracings, demonstrated strong correlations with fetal ABB variables (pH, BE, pCO2, sO2).
• The WAS index provides a continuous assessment, predicting cord blood pH within clinically relevant limits.

Conclusions:

• The WAS index effectively utilizes FHR characteristics across different fetal behavioral states for continuous ABB assessment.
• The WAS index enables accurate prediction of fetal acid-base balance, offering a valuable diagnostic tool.
• This continuous FHR analysis method complements, rather than replaces, qualitative cardiotocography (CTG) analysis.