Fetal Heart Rate Monitoring Guidelines Updated

Laurie Barclay, MD

July 01, 2009

July 1, 2009 — The American College of Obstetricians and Gynecologists (ACOG) has refined its definitions, classifications, and interpretations of fetal heart rate (FHR) monitoring and published the revised version of its guidelines in the July issue of Obstetrics & Gynecology (ACOG Practice Bulletin #106).The revised recommendations are similar to those reached during the Eunice Kennedy Shriver National Institute of Child and Health Development workshop on electronic fetal monitoring (EFM) held in April 2008.

"Since 1980, the use of EFM has grown dramatically, from being used on 45% of pregnant women in labor to 85% in 2002," lead ACOG guidelines author George A. Macones, MD, said in a news release. "Although EFM is the most common obstetric procedure today, unfortunately it hasn't reduced perinatal mortality or the risk of cerebral palsy. In fact, the rate of cerebral palsy has essentially remained the same since World War II despite fetal monitoring and all of our advancements in treatments and interventions."

In addition to controversy regarding the efficacy of EFM, other concerns include interobserver and intraobserver variability, varying systems for interpretation, and management algorithms. Furthermore, studies suggest that use of EFM is linked to a higher rate of cesarean deliveries and operative vaginal deliveries.

Goals of Revised Guidelines

The purpose of FHR monitoring is to follow the status of the fetus during labor so that clinicians can intervene if there is evidence of fetal distress, as reflected in FHR above or below the normal range of 110 to 160 beats per minute (BPM), or in FHR that does not change in response to uterine contractions. The objective of the revised guidelines was to improve consistency of the use of common terminology and to reduce the wide variability in FHR interpretations.

"Our goal with the ACOG guidelines was to define existing terminology and narrow definitions and categories so that everyone is on the same page," Dr. Macones said.

EFM, which monitors FHR, the duration of uterine contractions, and the interval between uterine contractions, is the most commonly used method of FHR monitoring because it allows measurement of the FHR response to uterine contractions. Manual auscultation with a small, handheld Doppler device or a fetoscope is used less commonly for FHR monitoring.

To identify pertinent articles published in English between January 1985 and January 2009, the guidelines authors searched the MEDLINE database, the Cochrane Library, and ACOG's own internal resources and documents, as well as studies cited in bibliographies of identified articles.

Although articles reporting results of original research were given priority, the guidelines authors also consulted review articles and commentaries and guidelines published by organizations such as the National Institutes of Health. Abstracts of research presented at symposia and scientific conferences were excluded. Expert opinions from obstetrician-gynecologists were used for recommendations when no reliable research was available.

The revised guidelines now include a 3-tier classification system for FHR tracings, with category 1 FHR tracings characterized as normal and requiring no specific intervention. Category 2 tracings are classified as indeterminate, mandating further workup, surveillance, and possibly additional tests to further evaluate fetal health. Category 3 tracings are characterized as abnormal and require immediate intervention, such as providing oxygen to the mother, changing her position, stopping labor stimulation, treating maternal hypotension, or initiating prompt delivery if the tracings do not return to normal.

Several types of medications used during labor and delivery may affect FHR. All narcotics decrease FHR variability as well as the frequency of accelerations. Butorphanol causes a transient sinusoidal FHR pattern and slightly increases mean heart rate vs meperidine. Cocaine use reduces long-term FHR variability.

Betamethasone, but not dexamethasone, decreases FHR variability. Particularly when used at more than 29 weeks of gestation, corticosteroids abolish diurnal fetal rhythms. Magnesium sulfate significantly reduces short-term FHR variability, produces a clinically insignificant decrease in FHR, and inhibits the increase in accelerations with advancing gestational age. Terbutaline increases baseline FHR and the incidence of fetal tachycardia, but zidovudine is not known to affect the FHR baseline, variability, or number of accelerations or decelerations.

Clinical Recommendations

Specific clinical recommendations and conclusions in the revised ACOG guidelines that are based on good and consistent scientific evidence (level A) include the following:

• The false-positive rate of EFM for predicting cerebral palsy exceeds 99%.

• The use of EFM is linked to higher rates of both vacuum and forceps operative vaginal delivery, as well as of cesarean delivery for abnormal FHR patterns and/or acidosis.

• Recurrent variable decelerations on the FHR tracing should lead to consideration of amnioinfusion to relieve umbilical cord compression.

• For assessing fetal status, pulse oximetry has not been shown to be clinically useful.

Specific clinical recommendations and conclusions in the revised ACOG guidelines that are based on inconsistent scientific evidence (level B) include the following:

• Interpretation of FHR tracing is subject to high interobserver and intraobserver variability.

• Reinterpretation of the FHR tracing may not be reliable, especially once the neonatal outcome is known.

• Use of EFM is not associated with a lower incidence of cerebral palsy.

Specific clinical recommendations based on expert opinion (level C) include the following:

• A 3-tiered system is recommended to categorize FHR patterns.

• During labor, women with high-risk conditions should undergo continuous FHR monitoring.

• Preferred nomenclature should be changed so that the terms hyperstimulation and hypercontractility are no longer used.

"When EFM is used during labor, the nurses or physicians should review it frequently," the guidelines authors conclude. "In a patient without complications, the FHR tracing should be reviewed approximately every 30 minutes in the first stage of labor and every 15 minutes during the second stage. The corresponding frequency for patients with complications (eg, fetal growth restriction, preeclampsia) is approximately every 15 minutes in the first stage of labor and every 5 minutes during the second stage."

Obstet Gynecol. 2009;114:192-202.

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