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Am J Perinatol
DOI: 10.1055/a-2601-8862
Original Article

Proportion of Time in Category II Fetal Heart Rate Tracing and Adverse Outcomes

Kristen A. Cagino 
1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston, Houston, Texas
,
Rachel L. Wiley 
2   Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California San Diego, San Diego, California
,
Aaron W. Roberts 
1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston, Houston, Texas
,
Fabrizio Zullo 
3   Department of Department of Maternal and Child Health and Urological Sciences, Sapienza University of Rome, Rome, Italy
,
Hector Mendez-Figueroa
1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston, Houston, Texas
,
Suneet P. Chauhan
4   Delaware Center for Maternal-Fetal Medicine of Christiana Care, Newark, Delaware
› Author Affiliations Funding None.
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Abstract

Objective

The primary objective was to ascertain if the proportion of time in category II fetal heart rate tracing (FHRT) prior to birth among term (≥ 37 weeks) singletons in labor was associated with composite adverse neonatal outcomes (CANO).

Study Design

The inclusion criteria for this retrospective cohort study were nonanomalous singletons at term, whose FHRT was reviewed by obstetricians blinded to the maternal characteristics and neonatal outcomes. According to ACOG's criteria, the last 20 to 120 minutes of the tracing were reviewed in 20-minute epochs. The cohorts were divided into three groups: group A, category II for < 33% of the available tracing; group B, for ≥ 33 and <66%; and, group C, for ≥ 66% of the FHRT. CANO was any of the following: Apgar score < 7 at 5 minutes, mechanical ventilation, hypoxic-ischemic encephalopathy, neonatal seizure, confirmed sepsis, or neonatal death. Group A was compared with groups B and C, using an adjusted odds ratio (aOR).

Results

FHRT for 5,160 consecutive deliveries was reviewed, and 2,780 (53.8%) met the inclusion criteria. Of the 321,980 minutes of FHRT reviewed, 223,000 minutes (69.2%) were category II. The overall CANO among the cohorts was 1.4% (38/2,780), and it did not vary significantly between group A versus B (aOR: 1.11; 95% confidence interval [CI]: 0.35–3.48), or between group A versus C (aOR: 0.80; 95% CI: 0.27–2.35). The overall rate of cesarean delivery for nonreassuring FHRT was 9.7% (270/2,780), and it did not differ between group A versus B (aOR: 0.86; 95% CI: 0.51–1.47) or group A versus C (aOR: 1.18; 95% CI: 0.73–1.91).

Conclusion

Among term deliveries, in the last 20 to 120 minutes before birth, 70% of the time FHRT was category II, and the proportion of time in Category II did not significantly influence adverse neonatal outcomes.

Key Points

  • In the last 20 to 120 minutes before birth, 69.2% of FHRT were category II.

  • In 2,780 parturients with category II FHRT, CANO occurred in 1.4%.

  • Category II FHRT, for 20 to 120 min before birth, was not assocated with adverse outcomes

Keywords

Apgar score - nonreassuring fetal heart rate tracing - late deceleration - prolonged deceleration - variable decelerations - neonatal morbidity - maternal morbidity

Supplementary Material



Publication History

Received: 27 April 2025

Accepted: 07 May 2025

Accepted Manuscript online:
07 May 2025

Article published online:
21 May 2025

© 2025. Thieme. All rights reserved.

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