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Intrapartum Fetal Heart Rate Tracing Among Small-for-Gestational Age Compared With Appropriate-for-Gestational-Age Neonates

Chauhan, Suneet P., MD, DSc (Hon); Weiner, Steven J., MS; Saade, George R., MD; Belfort, Michael A., MD, PhD; Reddy, Uma M., MD, MPH; Thorp, John M. Jr, MD; Tita, Alan T. N., MD, PhD; Miller, Russell S., MD; Dinsmoor, Mara J., MD, MPH; McKenna, David S., MD; Stetzer, Bradley, DO; Rouse, Dwight J., MD; Gibbs, Ronald S., MD; El-Sayed, Yasser Y., MD; Sorokin, Yoram, MD; Caritis, Steve N., MD for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network

doi: 10.1097/AOG.0000000000002855
Contents: Labor: Original Research

OBJECTIVE: To compare fetal heart rate (FHR) patterns during the last hour of labor between small-for-gestational-age (SGA; birth weight less than the 10th percentile for gestational age) and appropriate-for-gestational-age (AGA; birth weight at the 10–90th percentile) neonates at 36 weeks of gestation or greater. We also compared the rate of cesarean delivery and composite neonatal morbidity among SGA and AGA newborns.

METHODS: This is a secondary analysis of a randomized trial of intrapartum fetal electrocardiographic ST-segment analysis. We excluded women with chorioamnionitis, insufficient duration of FHR tracing in the hour before delivery, and anomalous newborns. Fetal heart rate patterns were categorized by computerized pattern recognition software (PeriCALM Patterns). Composite neonatal morbidity was defined as any of the following: intrapartum fetal death, Apgar score 3 or less at 5 minutes, cord artery pH 7.05 or less, base deficit 12 mmol/L or greater, neonatal seizure, intubation at delivery, neonatal encephalopathy, and neonatal death. Logistic regression was used to evaluate the association between FHR patterns and SGA adjusted for magnesium sulfate exposure and stage of labor.

RESULTS: Of the 11,108 women randomized, 85% (n=9,402) met inclusion criteria, of whom 9% were SGA. In the last hour, the likelihood of accelerations was significantly lower among SGA than AGA neonates (72.4% vs 66.8%; P=.001). Variable decelerations lasting greater than 60 seconds, with depth greater than 60 beats per minute (bpm) or nadir less than 60 bpm, were significantly more common with SGA than AGA (all P<.001). The rate of late decelerations, prolonged decelerations, or bradycardia were similar between SGA and AGA (all P>.05). Cesarean delivery for fetal indications was significantly more common with SGA (7.0%) than AGA (4.0%; P<.001). The composite neonatal morbidity was 1.4% among SGA and 1.0% among AGA (odds ratio 1.40, 95% CI 0.74–2.64).

CONCLUSION: Although the FHR patterns in the last hour of labor differ among SGA and AGA neonates, as does the rate of cesarean delivery, the composite neonatal morbidity was similar.

The rate of variable decelerations in the last hour of labor differed significantly between small compared with appropriate for gestational age, but the composite neonatal morbidity was similar.

Departments of Obstetrics and Gynecology, University of Texas Health Science Center at Houston, McGovern Medical School–Children's Memorial Hermann Hospital, Houston, Texas; University of Texas Medical Branch, Galveston, Texas; University of Utah Health Sciences Center, Salt Lake City, Utah; University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; University of Alabama at Birmingham, Birmingham, Alabama; Columbia University, New York, New York; Northwestern University, Chicago, Illinois; The Ohio State University, Columbus, Ohio; MetroHealth Medical Center–Case Western Reserve University, Cleveland, Ohio; Brown University, Providence, Rhode Island; University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado; Stanford University, Stanford, California; Wayne State University, Detroit, Michigan; and University of Pittsburgh, Pittsburgh, Pennsylvania; the George Washington University Biostatistics Center, Washington, DC; and the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland.

Corresponding author: Suneet P. Chauhan, MD, DSc (Hon), McGovern Medical School at The University of Texas Health Science Center at Houston, Department of Obstetrics, Gynecology and Reproductive Sciences, Division of Maternal-Fetal Medicine, 6431 Fannin Street, MSB 3.286, Houston, TX 77030; email:

The project described was supported by grants from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (HD34208, HD53097, HD40545, HD40560, HD27869, HD40485, HD40512, HD27915, HD40544, HD40500, HD68282, HD68268, HD27917, HD21410, HD36801) and by funding from Neoventa Medical. Comments and views expressed in this article are those of the authors and do not necessarily represent views of the NICHD. Neoventa Medical did not participate in the monitoring of the study; data collection, management, or analysis; or manuscript preparation.

Financial Disclosure The authors did not report any potential conflicts of interest.

Presented as an abstract at the annual meeting of Society of Maternal-Fetal Medicine, January 23–28, 2017, Las Vegas, Nevada.

* For a list of other members of the NICHD MFMU Network, see Appendix 1, available online at

The authors thank Kim Hill, RN, BSN, and Ashley Salazar, RN, MSN, WHNP, for assistance with protocol development and coordination between clinical research centers; Elizabeth Thom, PhD, for protocol development and oversight; and Michael W. Varner, MD, Sean C. Blackwell, MD, and Catherine Y. Spong, MD, for protocol development, oversight, and outcome review.

Dwight J. Rouse, MD, Associate Editor for Obstetrics, was not involved in the review of or decision to publish this article.

Each author has indicated that he or she has met the journal's requirements for authorship.

Received March 02, 2018

Received in revised form May 29, 2018

Accepted June 14, 2018

© 2018 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.