The 5-tier system of assessing fetal heart rate tracings is superior to the 3-tier system in identifying fetal acidemia

Objective: Electronic fetal heart rate monitoring was developed to identify fetuses at risk of acidemia for intervention before adverse outcomes. Our objective was to compare the 3-tier system with a 5-tier system in evaluation of fetal acidemia.

Study design: Retrospective case-control study of patients with a fetal arterial pH <7 matched to the next birth that resulted in a pH >7.2. Tracings were categorized into 3- and 5-tier systems by a single reviewer. Sensitivities and specificities were calculated for each.

Results: Twenty-four cases and 24 controls were identified. The sensitivity for an orange or red tracing was higher than for category III, with more of these in the pH <7 group compared with controls (P ≤ .001). There were significantly more green, blue, and yellow tracings in the normal pH group compared with the pH <7 group (P = .033, P = .008, P = .023), respectively.

Conclusion: The 5-tier system had a better sensitivity than the 3-tier system.