1. Current Commentary
The 2008 National Institute of Child Health
and Human Development Workshop Report
on Electronic Fetal Monitoring
Update on Definitions, Interpretation, and Research Guidelines
George A. Macones, MD, Gary D. V. Hankins, MD, Catherine Y. Spong, MD, John Hauth, MD,
and Thomas Moore, MD
and Gynecologists, and the Society management of intrapartum fetal
In April 2008, the Eunice Kennedy
for Maternal-Fetal Medicine part- compromise.
Shriver National Institute of Child
nered to sponsor a 2-day workshop The definitions agreed upon in
Health and Human Development, the
to revisit nomenclature, interpreta- that workshop were endorsed for
American College of Obstetricians
tion, and research recommendations clinical use in the most recent Amer-
for intrapartum electronic fetal heart
ican College of Obstetricians and
See related editorial on page 506. rate monitoring. Participants included
Gynecologists (ACOG) Practice Bul-
obstetric experts and representatives
letin in 2005 and also endorsed by
From the Department of Obstetrics and Gynecology, from relevant stakeholder groups and
Washington University in St. Louis, St. Louis, organizations. This article provides a
the Association of Women’s Health,
Missouri; Department of Obstetrics and Gynecology, summary of the discussions at the Obstetric and Neonatal Nurses.2
University of Texas Medical Branch, Galveston,
workshop. This includes a discussion Subsequently, the Royal College of
Texas; Eunice Kennedy Shriver National Institute of
Child Health and Human Development, Bethesda, of terminology and nomenclature for Obstetricians and Gynaecologists
Maryland; Department of Obstetrics and Gynecol- the description of fetal heart tracings (RCOG, 2001) and the Society of
ogy, University of Alabama at Birmingham, Bir- and uterine contractions for use in Obstetricians and Gynaecologists of
mingham, Alabama; and Department of Obstetrics
and Gynecology, University of California at San clinical practice and research. A Canada (SOGC, 2007) convened ex-
Diego, San Diego, California. three-tier system for fetal heart rate pert groups to assess the evidence-
For a list of workshop participants, see the Appendix tracing interpretation is also de- based use of electronic fetal monitor-
online at www.greenjournal.org/cgi/content/full/112/ scribed. Lastly, prioritized topics for ing (EFM). These groups produced
3/661/DC1. future research are provided. consensus documents with more
The workshop was jointly sponsored by the American (Obstet Gynecol 2008;112:661–6)
College of Obstetricians and Gynecologists, the Eu-
specific recommendations for FHR
nice Kennedy Shriver National Institute of Child pattern classification and intrapar-
Health and Human Development, and the Society for tum management actions.3,4 In addi-
Maternal-Fetal Medicine.
The recommendations from the National Institute of
Child Health and Human Development 2008
T he Eunice Kennedy Shriver Na-
tional Institute of Child Health
and Human Development (NICHD)
tion, new interpretations and defini-
tions have been proposed, includ-
Workshop are being published simultaneously by ing terminology such as “tachysys-
convened a series of workshops in
Obstetrics & Gynecology and the Journal of tole” and “hyperstimulation” and
Obstetric, Gynecologic, & Neonatal Nursing. the mid- 1990s to develop standard- new interpretative systems using
Corresponding author: George A. Macones, MD, ized and unambiguous definitions three and five tiers.3–5 The SOGC
Chair, Department of Obstetrics and Gynecology, for fetal heart rate (FHR) tracings,
Washington University in St Louis, MI 63110; Consensus Guidelines for Fetal
e-mail: maconesg@wustl.edu. culminating in a publication of rec- Health Surveillance presents a
Financial Disclosure ommendations for defining fetal three-tier system (normal, atypical,
The authors have no potential conflicts of interest to heart rate characteristics.1 The goal abnormal), as does RCOG.3,4 Parer
disclose. of these definitions was to allow the and Ikeda5 recently suggested a
© 2008 by The American College of Obstetricians predictive value of monitoring to five-tier management grading sys-
and Gynecologists. Published by Lippincott Williams
& Wilkins. be assessed more meaningfully and tem. Recently, the NICHD, ACOG,
ISSN: 0029-7844/08 to allow evidence-based clinical and the Society for Maternal-Fetal
VOL. 112, NO. 3, SEPTEMBER 2008 OBSTETRICS & GYNECOLOGY 661

2. Medicine jointly sponsored a work- E. The characteristics to be de- L. A full description of an EFM
shop focused on EFM. The goals of fined are those commonly used tracing requires a qualitative
this workshop were 1) to review and in clinical practice and research and quantitative description of:
update the definitions for FHR pat- communications. 1. Uterine contractions.
tern categorization from the prior F. The features of FHR patterns 2. Baseline fetal heart rate.
workshop; 2) to assess existing clas- are categorized as either base- 3. Baseline FHR variability.
sification systems for interpreting line, periodic, or episodic. Peri- 4. Presence of accelerations.
specific FHR patterns and to make odic patterns are those associ- 5. Periodic or episodic deceler-
recommendations about a system for ated with uterine contractions, ations.
use in the United States; and 3) to and episodic patterns are those 6. Changes or trends of FHR
make recommendations for research not associated with uterine con- patterns over time.
priorities for EFM. Thus, while goals tractions.
Uterine contractions are quanti-
1 and 3 are similar to the prior G. The periodic patterns are distin- fied as the number of contractions
workshop, a new emphasis on inter- guished on the basis of wave- present in a 10-minute window,
pretative systems (goal 2) was part of form, currently accepted as ei- averaged over 30 minutes. Con-
the recent workshop. ther “abrupt” or “gradual” onset. traction frequency alone is a partial
As was true in the prior publica- H. Accelerations and decelera- assessment of uterine activity.
tion,1 before presenting actual defini- tions are generally determined Other factors such as duration, in-
tions and interpretation, it is neces- in reference to the adjacent tensity, and relaxation time be-
sary to state a number of assumptions baseline FHR. tween contractions are equally im-
and factors common to FHR inter- I. No distinction is made between portant in clinical practice.
pretation in the United States. short-term variability (or beat- The following represents termi-
These were defined in the initial to-beat variability or R–R wave nology to describe uterine activity:
publication1 and were affirmed period differences in the elec-
and/or updated by the panel: trocardiogram) and long-term A. Normal: 5 contractions in 10
variability, because in actual minutes, averaged over a 30-
A. The definitions are primarily practice they are visually deter- minute window.
developed for visual interpreta- mined as a unit. Hence, the B. Tachysystole: 5 contractions in
tion of FHR patterns. However, definition of variability is based 10 minutes, averaged over a
it is recognized that computer- visually on the amplitude of the 30-minute window.
ized interpretation is being de- complexes, with exclusion of C. Characteristics of uterine contractions:
veloped and the definitions the sinusoidal pattern. • Tachysystole should always
must also be adaptable to such J. There is good evidence that a be qualified as to the pres-
applications. number of characteristics of ence or absence of associated
B. The definitions apply to the in- FHR patterns are dependent FHR decelerations.
terpretations of patterns pro- upon fetal gestational age and • The term tachysystole ap-
duced from either a direct fetal physiologic status as well as ma- plies to both spontaneous or
electrode detecting the fetal stimulated labor. The clinical
ternal physiologic status. Thus,
response to tachysystole may
electrocardiogram or an exter- FHR tracings should be evalu-
differ depending on whether
nal Doppler device detecting ated in the context of many
contractions are spontaneous
the fetal heart rate events with clinical conditions including
or stimulated.
use of the autocorrelation tech- gestational age, prior results of
• The terms hyperstimulation
nique. fetal assessment, medications,
and hypercontractility are
C. The record of both the FHR maternal medical conditions,
not defined and should be
and uterine activity should be and fetal conditions (eg, growth abandoned.
of adequate quality for visual restriction, known congenital
interpretation. anomalies, fetal anemia, ar- Fetal heart rate patterns are de-
D. The prime emphasis in this re- rhythmia, etc). fined by the characteristics of base-
port is on intrapartum patterns. K. The individual components of line, variability, accelerations, and
The definitions may also be ap- defined FHR patterns do not decelerations.
plicable to antepartum observa- occur independently and gen- The baseline FHR is determined
tions. erally evolve over time. by approximating the mean FHR
662 Macones et al Electronic Fetal Heart Rate Monitoring OBSTETRICS & GYNECOLOGY

3. rounded to increments of 5 beats Decelerations are classified as curring with 50% of uterine con-
per minute (bpm) during a 10- late, early, or variable based on tractions in any 20-minute segment
minute window, excluding acceler- specific characteristics (see the Box, are defined as intermittent.
ations and decelerations and peri- “Characteristics of Decelerations”).
ods of marked FHR variability Variable decelerations may be ac-
( 25 bpm). There must be at least companied by other characteris- General Considerations for
2 minutes of identifiable baseline tics, the clinical significance of the Interpretation of Fetal
segments (not necessarily contigu- which requires further research in- Heart Rate Patterns
ous) in any 10-minute window, or vestigation. Some examples in- A variety of systems for EFM
the baseline for that period is inde- clude a slow return of the FHR after interpretation have been devel-
terminate. In such cases, it may be the end of the contraction, biphasic oped and propagated in the
necessary to refer to the previous decelerations, tachycardia after vari- United States and worldwide.3–5
10-minute window for determina- able deceleration(s), accelerations Any interpretation system must
tion of the baseline. Abnormal preceding and/or following, some- be based, to the greatest extent
baseline is termed bradycardia when times called “shoulders” or “over- possible, on existing evidence
the baseline FHR is 110 bpm; it is shoots,” and fluctuations in the FHR (recognizing that in some areas
termed tachycardia when the base- in the trough of the deceleration. evidence is lacking). In addition,
line FHR is 160 bpm. A prolonged deceleration is any system should be simple and
Baseline FHR variability is deter- present when there is a visually applicable to clinical practice.
mined in a 10-minute window, ex- apparent decrease in FHR from the Given that the fetal heart rate
cluding accelerations and decelera- baseline that is 15 bpm, lasting response is a dynamic process, and
tions. Baseline FHR variability is 2 minutes, but 10 minutes. A one that evolves over time, the
defined as fluctuations in the base- deceleration that lasts 10 minutes categories of FHR patterns are dy-
line FHR that are irregular in ampli- is a baseline change. namic and transient, requiring fre-
tude and frequency. The fluctuations A sinusoidal fetal heart rate pattern quent reassessment. It is common
are visually quantitated as the ampli- is a specific fetal heart rate pattern for FHR tracings to move from one
tude of the peak-to-trough in bpm. that is defined as having a visually category to another over time.
Variability is classified as fol- apparent, smooth, sine wave–like The FHR tracing should be in-
lows: Absent FHR variability: am- undulating pattern in FHR baseline terpreted in the context of the over-
plitude range undetectable. Mini- with a cycle frequency of 3–5/min all clinical circumstances, and cate-
mal FHR variability: amplitude that persists for 20 minutes. gorization of a FHR tracing is
range undetectable and 5 bpm. limited to the time period being
Moderate FHR variability: amplitude assessed. The presence of FHR ac-
range 6 bpm to 25 bpm. Marked Quantitation of Decelerations celerations (either spontaneous or
FHR variability: amplitude range The magnitude of a deceleration is stimulated) reliably predicts the ab-
25 bpm. quantitated by the depth of the nadir sence of fetal metabolic acidemia.
An acceleration is a visually ap- in beats per minute (excluding tran- The absence of accelerations does
parent abrupt increase in FHR. An sient spikes or electronic artifact). not, however, reliably predict fetal
abrupt increase is defined as an The duration is quantitated in min- acidemia. Fetal heart rate accelera-
increase from the onset of acceler- utes and seconds from the beginning tions can be stimulated with a vari-
ation to the peak in 30 seconds. to the end of the deceleration. Accel- ety of methods (vibroacoustic,
To be called an acceleration, the erations are quantitated similarly. transabdominal halogen light, and
peak must be 15 bpm, and the Some authors have suggested direct fetal scalp stimulation).
acceleration must last 15 seconds grading of decelerations based on Moderate FHR variability reli-
from the onset to return. A pro- the depth of the deceleration or ably predicts the absence of fetal
longed acceleration is 2 minutes absolute nadir in beats per minute metabolic acidemia at the time it is
but 10 minutes in duration. Fi- and duration.4 –7 These grading sys- observed. Minimal or absent FHR
nally, an acceleration lasting 10 tems require further investigation variability alone does not reliably
minutes is defined as a baseline as to their predictive value. predict the presence of fetal hypox-
change. Before 32 weeks of gesta- Decelerations are defined as re- emia or metabolic acidemia. The
tion, accelerations are defined as current if they occur with 50% of significance of marked FHR (previ-
having a peak 10 bpm and a uterine contractions in any 20- ously described as saltatory) vari-
duration of 10 seconds. minute window. Decelerations oc- ability is unclear.
VOL. 112, NO. 3, SEPTEMBER 2008 Macones et al Electronic Fetal Heart Rate Monitoring 663

4. Characteristics of Decelerations
Late Deceleration
• Visually apparent usually symmetrical gradual decrease and return of the fetal heart rate (FHR)
associated with a uterine contraction.
• A gradual FHR decrease is defined as from the onset to the FHR nadir of 30 seconds.
• The decrease in FHR is calculated from the onset to the nadir of the deceleration.
• The deceleration is delayed in timing, with the nadir of the deceleration occurring after the peak of
the contraction.
• In most cases, the onset, nadir, and recovery of the deceleration occur after the beginning, peak, and
ending of the contraction, respectively.
Early Deceleration
• Visually apparent, usually symmetrical, gradual decrease and return of the FHR associated with
a uterine contraction.
• A gradual FHR decrease is defined as one from the onset to the FHR nadir of 30 seconds.
• The decrease in FHR is calculated from the onset to the nadir of the deceleration.
• The nadir of the deceleration occurs at the same time as the peak of the contraction.
• In most cases the onset, nadir, and recovery of the deceleration are coincident with the beginning,
peak, and ending of the contraction, respectively.
Variable Deceleration
• Visually apparent abrupt decrease in FHR.
• An abrupt FHR decrease is defined as from the onset of the deceleration to the beginning of the FHR nadir
of 30 seconds. The decrease in FHR is calculated from the onset to the nadir of the deceleration.
• The decrease in FHR is 15 beats per minute, lasting 15 seconds, and 2 minutes in duration.
• When variable decelerations are associated with uterine contractions, their onset, depth, and duration commonly
vary with successive uterine contractions.
Interpretation of Fetal Heart tracing may move back and forth into account the entire associated
Rate Patterns between categories depending on clinical circumstances.
Based on careful review of the the clinical situation and manage- Category III FHR tracings are
available options, a three-tier sys- ment strategies employed. abnormal. Category III tracings are
tem for the categorization of FHR Category I FHR tracings are predictive of abnormal fetal acid–
patterns is recommended (see the normal. Category I FHR tracings base status at the time of observa-
Box, “Three-Tier Fetal Heart Rate are strongly predictive of normal tion. Category III FHR tracings
Interpretation System”). Although fetal acid– base status at the time require prompt evaluation. De-
the development of management of observation. Category I FHR pending on the clinical situation,
algorithms is a function of profes- tracings may be followed in a efforts to expeditiously resolve the
sional specialty entities, some gen- routine manner, and no specific abnormal FHR pattern may include,
eral management principles were action is required. but are not limited to, provision of
Category II FHR tracings are in- maternal oxygen, change in mater-
agreed upon for these categories.
determinate. Category II FHR trac- nal position, discontinuation of la-
Fetal heart rate tracing patterns
ings are not predictive of abnormal bor stimulation, and treatment of
provide information on the current
fetal acid– base status, yet we do not maternal hypotension.
acid– base status of the fetus and
cannot predict the development of have adequate evidence at present to
cerebral palsy. Categorization of classify these as Category I or Cate- Research Recommendations
the FHR tracing evaluates the fetus gory III. Category II FHR tracings Since the last workshop, there has
at that point in time; tracing pat- require evaluation and continued not been a wealth of research on
terns can and will change. A FHR surveillance and reevaluation, taking EFM. With the high penetrance of
664 Macones et al Electronic Fetal Heart Rate Monitoring OBSTETRICS & GYNECOLOGY

5. Three-Tier Fetal Heart Rate Interpretation System
Category I
Category I fetal heart rate (FHR) tracings include all of the following:
• Baseline rate: 110 –160 beats per minute (bpm)
• Baseline FHR variability: moderate
• Late or variable decelerations: absent
• Early decelerations: present or absent
• Accelerations: present or absent
Category II
Category II FHR tracings include all FHR tracings not categorized as Category I or Category III. Category II
tracings may represent an appreciable fraction of those encountered in clinical care. Examples of Category II
FHR tracings include any of the following:
Baseline rate
• Bradycardia not accompanied by absent baseline variability
• Tachycardia
Baseline FHR variability
• Minimal baseline variability
• Absent baseline variability not accompanied by recurrent decelerations
• Marked baseline variability
Accelerations
• Absence of induced accelerations after fetal stimulation
Periodic or episodic decelerations
• Recurrent variable decelerations accompanied by minimal or moderate baseline variability
• Prolonged deceleration 2 minutes but 10 minutes
• Recurrent late decelerations with moderate baseline variability
• Variable decelerations with other characteristics, such as slow return to baseline, “overshoots,”
or “shoulders”
Category III
Category III FHR tracings include either:
• Absent baseline FHR variability and any of the following:
- Recurrent late decelerations
- Recurrent variable decelerations
- Bradycardia
• Sinusoidal pattern
this technology into obstetric prac- lationship to clinically relevant out- be focused on the effectiveness of
tice, well-designed studies are comes, and the effect of duration of educational programs on EFM that
needed to fill gaps in knowledge. patterns (eg, recurrent late deceler- include all relevant stakeholders.
Areas of highest priority for re- ations with minimal variability) on Although computerized interpreta-
search include observational stud- clinical outcomes. Other needed tion systems have not developed as
ies focused on indeterminate FHR studies include work that evaluates rapidly as anticipated, studies are
patterns, including descriptive epi- contraction frequency, strength, needed on the effectiveness of com-
demiology, frequency of specific and duration on FHR and clinical puterized compared with provider
patterns, change over time, the re- outcomes. Research also needs to interpretation, including the analy-
VOL. 112, NO. 3, SEPTEMBER 2008 Macones et al Electronic Fetal Heart Rate Monitoring 665

6. sis of existing data sets. Other areas 2. American College of Obstetricians and Canada, British Columbia Perinatal
Gynecologists. ACOG Practice Bulle- Health Program. Fetal health surveil-
for work include the development tin. Clinical Management Guidelines lance: antepartum and intrapartum con-
of new comprehensive data sets for Obstetrician–Gynecologists, Num- sensus guideline [published erratum
integrating outcomes with EFM in ber 70, December 2005 (Replaces Prac- appears in J Obstet Gynaecol Can
tice Bulletin Number 62, May 2005). 2007;29:909]. J Obstet Gynaecol Can
digitally addressable format and re- Intrapartum fetal heart rate monitoring. 2007;29 suppl:S3–56.
search on effectiveness of tech- Obstet Gynecol 2005;106:1453–60.
5. Parer JT, Ikeda T. A framework for
niques supplementary to EFM, 3. The use of electronic fetal monitoring: standardized management of intrapar-
the use and interpretation of cardioto- tum fetal heart rate patterns. Am J
such as ST segment analysis. cography in intrapartum fetal surveil- Obstet Gynecol 2007;197:26.e1–6.
lance. Evidence-based clinical guideline
number 8. Clinical Effectiveness Sup- 6. Chao A. Graphic mnemonic for variable
REFERENCES port Unit. London (UK): RCOG Press; decelerations. Am J Obstet Gynecol
1. Electronic Fetal Heart Rate Monitor- 2001. Available at: www.rcog.org.uk/ 1990;163:1098.
ing: research guidelines for interpreta- resources/public/pdf/efm_guideline_ 7. Parer JT, King T, Flanders S, Fox M,
tion. National Institute of Child Health final_2may2001.pdf. Retrieved June 30, Kilpatrick SJ. Fetal acidemia and elec-
and Human Development Research 2006. tronic fetal heart rate patterns: is there
Planning Workshop. Am J Obstet 4. Liston R, Sawchuck D, Young D. Soci- evidence of an association? J Matern
Gynecol 1997;177:1385–90. ety of Obstetrics and Gynaecologists of Fetal Neonatal Med. 2006;19:289–94.
666 Macones et al Electronic Fetal Heart Rate Monitoring OBSTETRICS & GYNECOLOGY