Acog Tococardiografia

ACOG PRACTICE BULLETIN
CLINICAL MANAGEMENT GUIDELINES FOR OBSTETRICIAN–GYNECOLOGISTS
NUMBER 106, JULY 2009
Replaces Practice Bulletin Number 70, December 2005

Intrapartum Fetal Heart Rate Monitoring: Nomenclature, Interpretation, and General Management Principles
This Practice Bulletin was developed by the ACOG Committee on Practice Bulletins with the assistance of George A. Macones, MD.The information is designed to aid practitioners in making decisions about appropriate obstetric and gynecologic care. These guidelines should not be construed as dictating an exclusive course of treatment or procedure. Variations in practice may be warranted based on the needs of the individual patient, resources, and limitations unique to the institution or type of practice. In the most recentyear for which data are available, approximately 3.4 million fetuses (85% of approximately 4 million live births) in the United States were assessed with electronic fetal monitoring (EFM), making it the most common obstetric procedure (1). Despite its widespread use, there is controversy about the efficacy of EFM, interobserver and intraobserver variability, nomenclature, systems for interpretation,and management algorithms. Moreover, there is evidence that the use of EFM increases the rate of cesarean deliveries and operative vaginal deliveries. The purpose of this document is to review nomenclature for fetal heart rate assessment, review the data on the efficacy of EFM, delineate the strengths and shortcomings of EFM, and describe a system for EFM classification.

Background
A complexinterplay of antepartum complications, suboptimal uterine perfusion, placental dysfunction, and intrapartum events can result in adverse neonatal outcome. Known obstetric conditions, such as hypertensive disease, fetal growth restriction, and preterm birth, predispose fetuses to poor outcomes, but they account for a small proportion of asphyxial injury. In a study of term pregnancies with fetalasphyxia, 63% had no known risk factors (2). The fetal brain modulates the fetal heart rate through an interplay of sympathetic and parasympathetic forces. Thus, fetal heart rate (FHR) monitoring can be used to determine if a fetus is well oxygenated. It was used among 45% of laboring women in 1980, 62% in 1988, 74% in 1992, and 85% in 2002 (1).

THE AMERICAN COLLEGE OF OBSTETRICIANS ANDGYNECOLOGISTS WOMEN’S HEALTH CARE PHYSICIANS

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VOL. 114, NO. 1, JULY 2009

OBSTETRICS & GYNECOLOGY

Despite the frequency of its use, limitations of EFM include poor interobserver and intraobserver reliability, uncertain efficacy, and a high false-positive rate. Fetal heart rate monitoring may be performed externally or internally. Most external monitors use a Doppler device with computerizedlogic to interpret and count the Doppler signals. Internal FHR monitoring is accomplished with a fetal electrode, which is a spiral wire placed directly on the fetal scalp or other presenting part.

Characteristics of uterine contractions • The terms hyperstimulation and hypercontractility are not defined and should be abandoned. • Tachysystole should always be qualified as to the presence orabsence of associated FHR decelerations. • The term tachysystole applies to both spontaneous and stimulated labor. The clinical response to tachysystole may differ depending on whether contractions are spontaneous or stimulated. Table 1 provides EFM definitions and descriptions based on the 2008 National Institute of Child Health and Human Development Working Group findings. Decelerations aredefined as recurrent if they occur with at least one half of the contractions.

Guidelines for Nomenclature and Interpretation of Electronic Fetal Heart Rate Monitoring
In 2008, the Eunice Kennedy Shriver National Institute of Child Health and Human Development partnered with the American College of Obstetricians and Gynecologists and the Society for Maternal–Fetal Medicine to sponsor a workshop...