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Am J Perinatol
DOI: 10.1055/a-2729-1189
Original Article

Fetal Heart Rate Tracings and Adverse Outcomes among Term Small versus Appropriate for Gestational Age

Authors

  • Shareen Patel

    1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States

  • Kristen A. Cagino

    1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States

  • Aaron W. Roberts 

    1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States

  • Rachel L. Wiley 

    2   Department of Obstetrics, Gynecology and Reproductive Sciences, University of California San Diego, California, United States

  • Christina Cortes

    1   Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States

  • Fabrizio Zullo 

    3   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 The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States

  • Suneet P. Chauhan

    4   Delaware Center for Maternal Fetal Medicine of ChristianaCare, Newark, Delaware, United States

Funding Information The authors report no financial support or external funding.
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Abstract

Objective

This study aimed to compare the patterns of fetal heart rate tracings (FHRTs), and outcomes among individuals with small (birth weight [BW] <10% for gestational age [GA]; SGA) versus appropriate (BW at 10–89% for GA; AGA) newborns at term (≥37.0 weeks).

Study Design

Our retrospective cohort study included consecutive deliveries over 15 months at a level IV center. FHRTs were reviewed by obstetricians blinded to maternal and neonatal outcomes. The inclusion criteria were non-anomalous singletons, cataloged as SGA or AGA birth weight using Alexander et al's nomogram. In 20-minute segments, the last 120 minutes of tracing were characterized. Rates of cesarean delivery (CD) and composite neonatal adverse outcomes (CNAOs) were compared.

Results

Of 5,160 deliveries, 3,029 (58.7%) met the inclusion criteria, and among them, 422 (13.9%) were SGA and 2,607 (86.1%) AGA. There were no differences in FHRT baseline, variability, or accelerations. Compared to AGA, SGA was more likely to have prolonged decelerations (11.8 vs. 8.4%, p = 0.021), and recurrent decelerations with ≥50% of contractions (21.3 vs. 16.5%, p = 0.014). Overall, the presence of category II FHRT or not was similar between the SGA (91.2%) and AGA (88.5%; p = 0.097). Persistent category II FHRT was significantly more common among SGA (37.4%) than AGA (28.1%; aOR = 1.47; 95% CI: 1.47–1.82) newborns. The rate of CD for non-reassuring FHRT was similar among the two groups. CNAO occurred in 1.4% in both SGA and AGA neonates (p = 0.95).

Conclusion

In our cohort of those with fetal monitoring prior to delivery at ≥37 weeks, persistent category II FHRT at the end of labor was significantly more common in SGA compared to AGA neonates; however, composite neonatal morbidity did not differ between the two groups. Our analysis provides data for shared decision-making that among SGA newborns, abnormalities of FHRT are not linked with adverse outcomes.

Key Points

  • There were no differences in FHRT baseline, variability, or accelerations between AGA and SGA.

  • SGA was more likely to have prolonged decelerations and recurrent decelerations with ≥50% of contractions.

  • Persistent category II FHRT before delivery is significantly more common with SGA than AGA.

  • FHRT abnormalities, however, were not associated with CD for non-reassuring FHRT, or adverse outcomes.

Keywords

fetal heart rate tracings - small for gestational age - maternal outcomes - neonatal outcomes

Note

This study was presented at the SMFM 2025 January 30 to February 1 in Denver, Colorado, United States.




Publication History

Received: 28 August 2025

Accepted: 21 October 2025

Accepted Manuscript online:
24 October 2025

Article published online:
06 November 2025

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