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

Abstract

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