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Management of intrapartum category I, II, and III fetal heart rate tracings

Author
George Macones, MD, MSCE
Section Editor
Susan M Ramin, MD
Deputy Editor
Vanessa A Barss, MD, FACOG

INTRODUCTION

Because of high interobserver and intraobserver variability in the interpretation of fetal heart rate (FHR) tracings [1-3], the American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal-Fetal Medicine (SMFM), and the United States National Institute of Child Health and Human Development (NICHD) convened a workshop to standardize definitions and interpretation for electronic fetal monitoring (EFM), propose management guidelines, and develop research questions [4,5]. Major outputs from this workshop were a clear standard for FHR interpretation (table 1) and a three-tier system for the categorization of intrapartum EFM (table 2A). This system has been widely adopted in the United States and elsewhere, and is the basis for this topic.

FREQUENCY OF CATEGORY I, II, AND III TRACINGS

In a study of the intrapartum fetal heart rate (FHR) characteristics of over 48,000 patients with a singleton, non-anomalous fetus in term labor at 10 hospitals, category I patterns were observed at some point during labor in over 99 percent of tracings, category II patterns were observed at some point in 84 percent of tracings, and category III patterns were observed at some point in 0.1 percent of tracings [6]. Over the course of labor, the FHR pattern was category I 78 percent of the time, category II 22 percent of the time, and category III 0.004 percent of the time. In the two hours before delivery, category I tracings were less commonly observed, and both category II and category III tracings became more common.

CATEGORY I TRACINGS: DEFINITION AND MANAGEMENT

A category I tracing is defined by (waveform 1):

Baseline rate: 110 to 160 beats per minute (beats per minute [bpm])

Moderate baseline fetal heart rate (FHR) variability (amplitude 6 to 25 bpm)

          

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Literature review current through: Nov 2016. | This topic last updated: Tue Mar 29 00:00:00 GMT+00:00 2016.
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