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Moreover, there is evi- about appropriate obstetric and dence that the use of EFM increases the rate of cesarean deliveries and opera- gynecologic care. These guidelines tive vaginal deliveries. The purpose of this document is to review nomenclature should not be construed as dictating for fetal heart rate assessment, review the data on the efficacy of EFM, delin- an exclusive course of treatment or procedure.
Variations in practice eate the strengths and shortcomings of EFM, and describe a system for EFM may be warranted based on the classification. Background A complex interplay of antepartum complications, suboptimal uterine perfu- sion, placental dysfunction, and intrapartum events can result in adverse neona- tal 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.
Fetal heart rate monitoring may be performed exter- nally or internally. Internal FHR monitoring is accom- tions. The clinical response to tachy- systole may differ depending on whether contrac- Guidelines for Nomenclature and tions are spontaneous or stimulated.
Deceler- of Child Health and Human Development partnered with ations are defined as recurrent if they occur with at least the American College of Obstetricians and Gynecolo- one half of the contractions. This workshop gathered a diverse group of Rate Tracings investigators with expertise and interest in the field to accomplish three goals: 1 to review and update the def- A variety of systems for EFM interpretation have been initions for FHR pattern categorization from the prior used in the United States and worldwide 4—6.
Based on workshop; 2 to assess existing classification systems for careful review of the available options, a three-tiered interpreting specific FHR patterns and make recommen- system for the categorization of FHR patterns is recom- dations about a system for use in the United States; and mended see box.
It is important to recognize that FHR 3 to make recommendations for research priorities for tracing patterns provide information only on the current EFM.
A complete clinical understanding of EFM neces- acid—base status of the fetus. Categorization of the FHR sitates discussion of uterine contractions, baseline FHR tracing evaluates the fetus at that point in time; tracing rate and variability, presence of accelerations, periodic patterns can and will change.
An FHR tracing may move or episodic decelerations, and the changes in these char- back and forth between the categories depending on the acteristics over time.
A number of assumptions and fac- clinical situation and management strategies used. Category I FHR are central to the proposed system of nomenclature tracings are strongly predictive of normal fetal acid—base and interpretation 3. Two such assumptions are of par- status at the time of observation.
Category I FHR trac- ticular importance. First, the definitions are primarily ings may be monitored in a routine manner, and no spe- developed for visual interpretation of FHR patterns, but cific action is required.
Category intrapartum patterns, but also are applicable to antepar- II FHR tracings are not predictive of abnormal fetal tum observations. Contraction frequency alone is ued surveillance and reevaluation, taking into account a partial assessment of uterine activity.
Other factors the entire associated clinical circumstances. In some cir- such as duration, intensity, and relaxation time between cumstances, either ancillary tests to ensure fetal well- contractions are equally important in clinical practice.
Category III Normal: five contractions or less in 10 minutes, tracings are associated with abnormal fetal acid—base averaged over a minute window status at the time of observation. Depending on the clini- utes, averaged over a minute window cal situation, efforts to expeditiously resolve the 2 ACOG Practice Bulletin No. In this case, one may refer to the prior minute window for determination of baseline.
Abbreviation: FHR, fetal heart rate. The National Institute of Child Health and Human Development workshop report on electronic fetal mon- itoring: update on definitions, interpretation, and research guidelines. Obstet Gynecol ;—6. Category II cations, the FHR tracing should be reviewed approxi- tracings may represent an appreciable fraction of those mately every 30 minutes in the first stage of labor and encountered in clinical care.
Examples of Category II every 15 minutes during the second stage. Thus, the benefits of EFM are gauged from reports comparing it with intermittent auscultation. The relative risk [RR], 1. Two months later, suring FHR tracing is predictive of cerebral palsy. In another study, five birth weights of 2, g or more is 0. The obstetricians interpreted the tracings only one or two will develop cerebral palsy 9.
The interpretation of cardiotocograms is more con- Available data, although limited in quantity, suggest sistent when the tracing is normal With retrospec- that the use of EFM does not result in a reduction in cere- tive reviews, the foreknowledge of neonatal outcome may bral palsy 8.
Given the that the occurrence of cerebral palsy has been stable over same intrapartum tracing, a reviewer is more likely to time, despite the widespread introduction of EFM Given that the available data do not show a clear When should the very preterm fetus be benefit for the use of EFM over intermittent auscultation, monitored?
Logistically, it may not be feasible to adhere to The decision to monitor the very preterm fetus requires guidelines for how frequently the heart rate should be a discussion between the obstetrician, pediatrician, and auscultated. The most common estimated fetal weight, and other factors and issues reasons for unsuccessful intermittent auscultation related to mode of delivery.
If a patient undergoes a included the frequency of recording and the require- cesarean delivery for indications related to a preterm ments for recording.
The earliest gestational age all pregnancies. Most of the clinical trials that compare that this will occur may vary. The labor of women with high-risk conditions followed by tachycardia and minimal or absent baseline eg, suspected fetal growth restriction, preeclampsia, and variability If FHR abnormalities are per- There are no comparative data indicating the opti- sistent, intrauterine resuscitation, ancillary tests to mal frequency at which intermittent auscultation should ensure fetal well-being, and possibly delivery should be be performed in the absence of risk factors.
One method undertaken Some show no inde- rate? In general, however, caution should be used Fetal heart rate patterns can be influenced by the med- in ascribing unfavorable findings on EFM to the use of ications administered in the intrapartum period. Most magnesium alone. Parenteral narcotics did have frequent contractions even when labor was also may affect the FHR.
A randomized trial comparing unstimulated As determined by computer analysis epidural anesthesia with 0. In antepartum regional analgesia A systematic review of accelerations Among twins those who did not receive epidural analgesia during labor 31 and singletons 32, 33 , the use of betamethasone There epidural anesthesia during labor.
An intent-to-treat also may be a decrease in the rate of accelerations with analysis of 1, laboring women randomized to com- the use of betamethasone. These changes, however, were bined spinal—epidural anesthesia 10 mcg of intrathecal not associated with increased obstetric interventions or sufentanil, followed by epidural bupivacaine and fen- with adverse outcomes The biologic mechanism of tanyl at the next request for analgesia or intravenous this is unknown.
Computerized analysis of the cardioto- meperidine 50 mg on demand, maximum mg in cograms indicates that use of dexamethasone is not asso- 4 hours noted a significantly higher rate of bradycar- ciated with a decrease in the FHR variability Neonatal outcome, however, was not normal fetal acid—base status? There are some methodological concerns with this study. The presence of FHR accelerations generally ensures that Another randomized controlled trial compared the the fetus is not acidemic.
The data relating FHR variabil- occurrence of FHR tracing abnormalities in laboring ity to clinical outcomes, however, are sparse. In this ability is strongly associated with an arterial umbilical study, FHR abnormalities were more common in cord pH higher than 7. One study reported that in women receiving combined spinal—epidural anesthesia the presence of late or variable decelerations, the umbili- Additional trials are necessary to determine the cal arterial pH was higher than 7. In anoth- epidural technique.
This been studied see Table 2. Of note, multiple regression study is limited because it did not consider other charac- analysis indicated that decreased variability attributed to teristics of the FHR tracing, such as the presence of accel- the use of magnesium sulfate was related to early gesta- erations or decelerations.
However, in most cases, normal tional age but not the serum magnesium level FHR variability provides reassurance about fetal status Studies report different findings with regard to the effect and the absence of metabolic acidemia. References 1. A comparison of the effects of epidural and meperidine analgesia during labor on fetal heart rate.
Obstet Gynecol ;—7. Intrapartum vibratory acoustic stimulation after maternal meperidine administra- tion.
Clin Exp Obstet Gynecol ;— Influence of meperidine on fetal movements and heart rate beat-to-beat variability in the active phase of labor. Am J Perinatol ;— Fetal response to maternally administered morphine.
Am J Obstet Gynecol ;— Fentanyl citrate analgesia during labor. Am J Obstet Gynecol ;—6. Therapeutic monitoring of nalbuphine: transplacental transfer and estimated pharmacokinetics in the neonate. Eur J Clin Pharmacol ;—9. Effect of labor analgesia with nalbuphine hydrochloride on fetal response to vibroacoustic stimulation.
J Reprod Med ;— Sinusoidal fetal heart rate pattern associated with butorphanol administration.
Fetal Heart Rate Monitoring During Labor