Strip of the Month: Pseudosinusoidal Pattern in Labor

Kafui A. Demasio

doi:10.1542/neo.20-8-e475

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Electronic Fetal Monitoring Case Review Series

Electronic fetal monitoring (EFM) is a popular technology used to establish fetal well-being. Despite its widespread use, the terminology used to describe patterns seen on the monitor has not been consistent until recently. In 1997, the National Institute of Child Health and Human Development (NICHD) Research Planning Workshop published guidelines for interpretation of fetal tracings. This publication was the culmination of 2 years of work by a panel of experts in the field of fetal monitoring and was endorsed in 2005 by both the American College of Obstetricians and Gynecologists (ACOG) and the Association of Women’s Health, Obstetric and Neonatal Nurses (AWHONN). In 2008, ACOG, NICHD, and the Society for Maternal-Fetal Medicine reviewed and updated the definitions for fetal heart rate (FHR) patterns, interpretation, and research recommendations. Following is a summary of the terminology definitions and assumptions found in the 2008 NICHD workshop report. Normal arterial umbilical cord gas values and indications of acidosis are defined in Table 1.

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Table.

Arterial Umbilical Cord Gas Values

Assumptions from the NICHD Workshop

Definitions are developed for visual interpretation, assuming that both the FHR and uterine activity recordings are of adequate quality
Definitions apply to tracings generated by internal or external monitoring devices
Periodic patterns are differentiated based on waveform, abrupt or gradual (eg, late decelerations have a gradual onset and variable decelerations have an abrupt onset)
Long- and short-term variability are evaluated visually as a unit
Gestational age of the fetus is considered when evaluating patterns
Components of FHR do not occur alone and generally evolve over time

Definitions

Baseline FHR

Approximate mean FHR rounded to increments of 5 beats/min in a 10-minute segment of tracing, excluding accelerations and decelerations, periods of marked variability, and segments of baseline that differ by >25 beats/min
In the 10-minute segment, the minimum baseline duration must be at least 2 minutes (not necessarily contiguous) …