Abstract
Objective
This study aimed to compare characteristics and categories of fetal heart rate tracings
(FHRT) among term (≥37.0 weeks) singletons without versus with composite adverse neonatal
outcomes (CANO).
Study Design
For 15 consecutive months, retrospectively FHRT of all deliveries were characterized
by obstetricians, who were blinded to maternal characteristics, intrapartum course,
and neonatal outcomes. The inclusion criteria were nonanomalous singletons at term,
who labored and had at least 20 minutes of FHRT. CANO included any of the following:
Apgar score < 7 at 5 minutes, mechanical ventilation for > 6 hours, hypoxic ischemic
encephalopathy, seizure, sepsis, bronchopulmonary dysplasia, intraventricular hemorrhage,
necrotizing, enterocolitis, birth injury, meconium aspiration syndrome, or neonatal
death. Positive likelihood ratios (PLR), with pre- and posttest probabilities, were
calculated.
Results
Of the 5,160 deliveries during the study period, 3,166 (61.4%) met inclusion criteria,
and 2,765 (87.3%) had between 20 and 120 minutes of FHRT reviewed. CANO occurred in
49 (1.5%) of the newborns. Three FHRT characteristics differed significantly among
those without and with CANO—severe decelerations, tachycardia with any decelerations,
or with severe decelerations. The PLR ranged from 1.60 to 5.96 for CANO, with posttest
probabilities of CANO from 2.4 to 8.3%. Persistent category I within 20 to 120 minutes
of delivery occurred with similar frequency among those without versus with CANO (11.5
vs. 8.2%; p = 0.472; PLR: 0.71). Presence of category II anytime occurred similarly for those
without and with CANO (88.5 vs. 89.8%; p = 0.785; PLR: 1.01); category III, at any time, also occurred similarly in the two
groups (0.8 vs. 2.0%; p = 0.319; PLR: 2.65).
Conclusion
In our cohorts of term singletons, neither the characteristics nor the category of
FHRT provided clinically meaningful discriminative capacity between newborns with
versus without CANO.
Key Points
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Category I FHRT in approximately 10% of parturients.
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At term, CANO in 1.5%.
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Characteristics of FHRT: poor diagnostic tests for CANO.
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Categories I, II, and III: similar frequencies with and without CANO.
Keywords
Apgar score - bradycardia - category I, II, or III - composite adverse neonatal outcomes
- decelerations—late, variable, prolonged - diagnostic tests - hypoxic ischemic encephalopathy
- likelihood ratio - tachycardia
