Graded classification of fetal heart rate tracings: association with neonatal metabolic acidosis and neurologic morbidity

Objective

The objective of the study was to measure the performance of a 5-tier, color-coded graded classification of electronic fetal monitoring (EFM).

Study Design

We used specialized software to analyze and categorize 7416 hours of EFM from term pregnancies. We measured how often and for how long each of the color-coded levels appeared in 3 groups of babies: (A) 60 babies with neonatal encephalopathy (NE) and umbilical artery base deficit (BD) levels were greater than 12 mmol/L; (I) 280 babies without NE but with BD greater than 12 mmol/L; and (N) 2132 babies with normal gases.

Results

The frequency and duration of EFM abnormalities considered more severe in the classification method were highest in group A and lowest in group N. Detecting an equivalent percentage of cases with adverse outcomes required only minutes spent with marked EFM abnormalities compared with much longer periods with lesser abnormalities.

Conclusion

Both degree and duration of tracing abnormality are related to outcome. We present empirical data quantifying that relationship in a systematic fashion.

Key words: computer analysis, electronic fetal monitoring, hypoxic ischemic encephalopathy, risk classification