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PRACTICE
BULLETIN
(Replaces Educational Bulletin Number 207, July 1995) Intrapartum Fetal Heart
Rate Monitoring
This Practice Bulletin wasdeveloped by the ACOG Com- In 2002, 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, interpretation of fetal heart rate George A. Macones, MD. Theinformation is designed to aid (FHR) patterns, reproducibility of its interpretation, and management algorithms for abnormal or nonreassuring patterns. Moreover, there is evidence that the use of EFM increases the rate of cesarean and operative vaginal deliveries. The pur- pose of this document is to review nomenclature for FHR assessment, review the data on the efficacy of EFM, delineate the strengths and shortcomings of EFM, and describe the management of nonreassuring FHR patterns. course of treatment or proce-dure. Variations in practice maybe warranted based on the Background
Even though the fetus is efficient at extracting oxygen from the maternal com- partment, a complex interplay of antepartum complications, suboptimal uterine perfusion, placental dysfunction, and intrapartum events may be associated with adverse outcome. Known obstetric conditions, such as hypertensive dis-ease, fetal growth restriction, and preterm birth, predispose fetuses to poor out-comes, but they account for a fraction of asphyxial injury. In a study of termpregnancies with fetal asphyxia, 63% had no known risk factors (2).
Monitoring the FHR is a modality intended to determine if a fetus is well oxygenated because the brain modulates the heart rate. It was used among 45%of parturients in 1980, 62% in 1988, 74% in 1992 (3), and 85% in 2002 (1).
Despite the frequency of its use, issues with EFM include poor interobserverand 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 computerized logic to interpret andcount the Doppler signals. Internal FHR monitoring is accomplished with afetal electrode, which is a spiral wire placed directly on the fetal scalp or otherpresenting part.
ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
Guidelines for Interpretation of
putative etiology of patterns or their relationship to hypox- Electronic Fetal Heart Rate Monitoring
emia or metabolic acidosis. The guidelines did not differ-entiate between short- and long-term variability because In 1997, the National Institute of Child Health and they are visually determined as one entity; however, they Human Development Research Planning Workshop gath- did encourage clinicians to take gestational age, medica- ered investigators with expertise in the field and proposed tions, prior fetal assessment, and obstetric and medical definitions for intrapartum FHR tracing (4). The underly- conditions into account when interpreting the FHR pat- ing assumptions of the definitions included that the FHR patterns, obtained either from a direct fetal electrode or A complete clinical understanding of the FHR neces- an external Doppler device, are for visual interpretation, sitates discussion of baseline rate, variability, presence of and that no a priori assumptions were made about the accelerations, periodic or episodic decelerations, and the Table 1. Definitions of Fetal Heart Rate Patterns
Definition
• The mean FHR rounded to increments of 5 beats per min during a 10 min segment, excluding: —Periodic or episodic changes—Periods of marked FHR variability—Segments of baseline that differ by more than 25 beats per min • The baseline must be for a minimum of 2 min in any 10-min segment • Fluctuations in the FHR of two cycles per min or greater• Variability is visually quantitated as the amplitude of peak-to-trough in beats per min —Absent—amplitude range undetectable—Minimal—amplitude range detectable but 5 beats per min or fewer—Moderate (normal)—amplitude range 6–25 beats per min—Marked—amplitude range greater than 25 beats per min • A visually apparent increase (onset to peak in less than 30 sec) in the FHR from the most recently • The duration of an acceleration is defined as the time from the initial change in FHR from the baseline • At 32 weeks of gestation and beyond, an acceleration has an acme of 15 beats per min or more above baseline, with a duration of 15 sec or more but less than 2 min • Before 32 weeks of gestation, an acceleration has an acme of 10 beats per min or more above baseline, with a duration of 10 sec or more but less than 2 min • Prolonged acceleration lasts 2 min or more but less than 10 min• If an acceleration lasts 10 min or longer, it is a baseline change • Baseline FHR less than 110 beats per min • In association with a uterine contraction, a visually apparent, gradual (onset to nadir 30 sec or more) • Nadir of the deceleration occurs at the same time as the peak of the contraction • In association with a uterine contraction, a visually apparent, gradual (onset to nadir 30 sec or more) • Onset, nadir, and recovery of the deceleration occur after the beginning, peak, and end of the • Baseline FHR greater than 160 beats per min • An abrupt (onset to nadir less than 30 sec), visually apparent decrease in the FHR below the baseline• The decrease in FHR is 15 beats per min or more, with a duration of 15 sec or more but less than 2 min • Visually apparent decrease in the FHR below the baseline• Deceleration is 15 beats per min or more, lasting 2 min or more but less than 10 min from onset to Abbreviation: FHR, fetal heart rate.
Reprinted from Am J Obstet Gynecol, Vol 177, Electronic fetal heart rate monitoring: research guidelines for interpretation, National Institute of Child Health and HumanDevelopment Research Planning Workshop, Pages 1385–90, Copyright 1997, with permission from Elsevier.
ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
OBSTETRICS & GYNECOLOGY
changes in these characteristics over time. Table 1 pro- • The use of EFM increased the use of both vacuum vides FHR pattern definitions and descriptions based on (OR 1.23, 95% CI, 1.02–1.49) and forceps (OR 2.4, National Institute of Child Health and Human Develop- 95% CI, 1.97–3.18) operative vaginal deliveries.
ment Working Group findings. Decelerations are quanti- • The use of EFM did not reduce overall perinatal fied by the depth of the nadir in beats per minute, as well mortality (OR 0.87, 95% CI, 0.57–1.33) although as the duration in minutes and seconds from the beginning perinatal mortality caused by fetal hypoxia appeared to the end of the deceleration. Accelerations are quantified to be reduced (OR 0.41, 95% CI, 0.17–0.98). It is similarly, whereas bradycardia and tachycardia are quan- important to recognize that for the comparison of titated by the actual FHR. Decelerations generally are perinatal mortality between EFM and intermittent defined as recurrent if they occur with at least one half of auscultation, the results presented are based on a small number of events; thus, the findings are statis- Guidelines for Review of Electronic
tically unstable. For example, for perinatal deaths Fetal Heart Rate Monitoring
caused by hypoxia, there were 17 deaths out of atotal of 9,163 fetuses in the intermittent auscultation When EFM is used during labor, the nurses or physicians group and seven out of 9,398 in the EFM group. If should review it frequently. In a patient without complica- there had been one fewer case of perinatal death in tions, the FHR tracing should be reviewed approximately the intermittent auscultation group, the results of the every 30 minutes in the first stage of labor and every meta-analysis for this outcome would not be statis- 15 minutes during the second stage. The corresponding fre- quency for patients with complications (eg, fetal growthrestriction, preeclampsia) is approximately every 15 min- There is an unrealistic expectation that a nonreas- utes in the first stage of labor and every 5 minutes during suring FHR tracing is predictive of cerebral palsy. The the second stage. Health care providers should periodical- positive predictive value of a nonreassuring pattern to ly document that they have reviewed the tracing. The FHR predict cerebral palsy among singleton newborns with tracing, as part of the medical record, should be labeled birth weights of 2,500 g or more is 0.14%, meaning that and available for review if the need arises. Computer stor- out of 1,000 fetuses with a nonreassuring FHR pattern, age of the FHR tracing that does not permit overwriting or only one or two will develop cerebral palsy (7). The revisions is reasonable, as is microfilm recording.
false-positive rate is extremely high, at greater than 99%.
Available data, although limited in size, suggest that EFM does not result in a reduction in cerebral palsy (3).
Clinical Considerations and
This is consistent with data that suggest that the occur- Recommendations
rence of cerebral palsy has been stable over time, despitethe widespread introduction of EFM (8). The principal How efficacious is electronic fetal heart rate
explanation for why the prevalence of cerebral palsy has monitoring?
not diminished despite the use of EFM is that 70% ofcases occur before the onset of labor; only 4% of The efficacy of EFM during labor is judged by its abil- encephalopathies can be attributed solely to intrapartum ity to decrease complications, such as neonatal seizures, cerebral palsy, or intrapartum fetal death, while mini- Given that the available data do not clearly support mizing the need for unnecessary obstetric interventions, EFM over intermittent auscultation, either option is such as operative vaginal or cesarean delivery. There are acceptable in a patient without complications. Logisti- no randomized clinical trials to compare the benefits of cally, it may not be feasible to adhere to guidelines for EFM with no form of monitoring during labor (5). Thus, how frequently the heart rate should be auscultated. One the benefits of EFM are gauged from reports comparing prospective study noted that the protocol for intermittent auscultation was successfully completed in only 3% of A meta-analysis synthesizing the findings of nine the cases (11). The most common reasons for unsuccess- randomized clinical trials comparing the modalities had ful intermittent auscultation included the frequency of recording and the requirements for recording.
• The use of EFM compared with intermittent auscul- Intermittent auscultation may not be appropriate for tation increased the overall cesarean delivery rate all pregnancies. Most of the clinical trials that compare (odds ratio [OR] 1.53, 95% confidence interval [CI], EFM with intermittent auscultation have excluded sub- 1.17–2.01) and the cesarean rate for suspected fetal jects at high risk for adverse outcomes, and the relative distress (OR 2.55, 95% CI, 1.81–3.53).
safety of intermittent auscultation in such cases is uncer- ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
tain. Those with high-risk conditions (eg, suspected fetal (19). Because preterm fetuses may be more susceptible to growth restriction, preeclampsia, and type 1 diabetes) intrapartum hypoxemia, they should be monitored. If FHR abnormalities are persistent, intrauterine resuscita- There are no comparative data indicating the optimal tion, ancillary tests to ensure fetal well-being, and possi- frequency at which intermittent auscultation should be bly delivery should be undertaken (20).
performed in the absence of risk factors. One method is to evaluate and record the FHR at least every 15 minutes What medications affect the fetal heart rate?
in the active phase of the first stage of labor and at leastevery 5 minutes in the second stage (12).
Fetal heart rate patterns can be influenced by the medica-tions administered in the intrapartum period. Most often, What is the interobserver and intraobserver
these changes are transient, although they sometimes variability of electronic fetal heart rate moni-
toring assessment?
Epidural analgesia with local anesthetic agents (lido- caine, bupivacaine) can lead to sympathetic blockade, There is a wide variation in the way obstetricians inter- maternal hypotension, transient uteroplacental insuffi- pret and respond to EFM tracings. When four obstetri- ciency, and alterations in the FHR. Parenteral narcotics cians, for example, examined 50 cardiotocograms, they also may affect the FHR. A randomized trial comparing agreed in only 22% of the cases (13). Two months later, epidural anesthesia with 0.25% of bupivacaine and during the second review of the same 50 tracings, the cli- intravenous meperidine reported that the beat-to-beat nicians interpreted 21% of the tracings differently than variability was decreased, and FHR accelerations were they did during the first evaluation (14). In another study, significantly less common with parenteral analgesia five obstetricians independently interpreted 150 cardio- compared with regional analgesia (21). The rates of decel- tocograms (15). The obstetricians interpreted the tracings erations and cesarean delivery for nonreassuring FHR trac- similarly in 29% of the cases, suggesting poor interob- ings were similar for the two groups. A systematic review of five randomized trials and seven observational studies An important factor that influences the interpretation also noted that the rate of cesarean delivery for nonreas- of cardiotocograms is whether the tracing is normal, suring FHR was similar between those who did and those equivocal, or ominous, with greater agreement if the trac- who did not receive epidural analgesia during labor (22).
ing is reassuring (16). With retrospective reviews, the Concern has been raised about combined spinal– foreknowledge of neonatal outcome may alter the epidural anesthesia during labor. An intent-to-treat reviewer’s impressions of the tracing. Given the same analysis of 1,223 parturients randomized to combined intrapartum tracing, a reviewer is more likely to find evi- spinal–epidural anesthesia (10 µg intrathecal sufentanil, dence of fetal hypoxia and criticize the obstetrician’s followed by epidural bupivacaine and fentanyl at the next management if the outcome was supposedly poor versus request for analgesia) or intravenous meperidine (50 mg on demand, maximum 200 mg in 4 hours) noted a signif- icantly higher rate of bradycardia and emergent cesarean Should the very preterm fetus be monitored?
delivery for nonreassuring abnormal FHR in the group The decision of whether to monitor the very preterm randomized to combined spinal–epidural anesthesia (23).
fetus is complicated. It requires a discussion between the Neonatal outcome, however, was not significantly differ- obstetrician, pediatrician, and patient concerning the ent between the two groups. There are methodologic con- likelihood of survival or severe morbidity of the preterm cerns with this study, and additional trials are necessary child (based on gestational age, estimated fetal weight, to determine the potential safety and efficacy of the com- and other factors) and issues related to mode of delivery.
bined spinal–epidural technique (22).
If a patient would undergo a cesarean delivery for The effect of corticosteroids, to enhance pulmonary fetal indications for a very preterm fetus, monitoring maturity of fetuses during preterm labor, on FHR has should be achieved continuously rather than intermittent- been studied (Table 2). Among twins (24) and singletons ly auscultated. The earliest gestational age that this will (25, 26), the use of betamethasone transiently decreased occur may vary by the institution. Nonreassuring FHR the FHR variability, which returned to pretreatment sta- patterns may occur with up to 60% of preterm parturi- tus by the fourth (25) to seventh (26) day. There also may ents, with the most common abnormality being decelera- be a decrease in the rate of accelerations with the use of tion and bradycardia, followed by tachycardia and a flat betamethasone. These changes, however, were not asso- tracing (18). Variable decelerations are more common ciated with increased obstetric interventions or with among preterm (55–70%) than term (20–30%) deliveries adverse outcomes (24). The biologic mechanism of this is ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
OBSTETRICS & GYNECOLOGY
Table 2. Effects of Medications on Fetal Heart Rate Patterns
Medications
Reference
Study Design
Effect on Fetal Heart Rate
Decrease in FHR variability with betamethasonebut not dexamethasone A significant decrease in the FHR baseline and variability; inhibits the increase in accelerations with advancing gestational age Decreased the number of accelerations, long- and short-term variation Abolishment or decrease in frequency of late and variable decelerations No difference in the FHR baseline, variability, number of accelerations or decelerations Abbreviation: FHR, fetal heart rate.
1Hatjis CG, Meis PJ. Sinusoidal fetal heart rate pattern associated with butorphanol administration. Obstet Gynecol 1986;67:377–80.
2Chazotte C, Forman L, Gandhi J. Heart rate patterns in fetuses exposed to cocaine. Obstet Gynecol 1991;78:323–5.
3Senat MV, Minoui S, Multon O, Fernandez H, Frydman R, Ville Y. Effect of dexamethasone and betamethasone on the fetal heart rate variability in preterm labour: arandomised study. Br J Obstet Gynaecol 1998;105:749–55.
4Hallak M, Martinez-Poyer J, Kruger ML, Hassan S, Blackwell SC, Sorokin Y. The effect of magnesium sulfate on fetal heart rate parameters: a randomized, placebo-con-trolled trial. Am J Obstet Gynecol 1999;181:1122–7.
5Wright JW, Ridgway LE, Wright BD, Covington DL, Bobitt JR. Effect of MgSO4 on heart rate monitoring in the preterm fetus. J Reprod Med 1996;41:605–8.
6Giannina G, Guzman ER, Lai YL, Lake MF, Cernadas M, Vintzileos AM. Comparison of the effects of meperidine and nalbuphine on intrapartum fetal heart rate trac-ings. Obstet Gynecol 1995;86:441–5.
7Kopecky EA, Ryan ML, Barrett JF, Seaward PG, Ryan G, Koren G, et al. Fetal response to maternally administered morphine. Am J Obstet Gynecol 2000;183:424–30.
8Tejani NA, Verma UL, Chatterjee S, Mittelmann S. Terbutaline in the management of acute intrapartum fetal acidosis. J Reprod Med 1983;28:857–61.
9Blackwell SC, Sahai A, Hassan SS, Treadwell MC, Tomlinson MW, Jones TB, et al. Effects of intrapartum zidovudine therapy on fetal heart rate parameters in womenwith human immunodeficiency virus infection. Fetal Diagn Ther 2001;16:413–6.
unknown. Computerized analysis of the cardiotocograms over 20 minutes (30). In antepartum patients, administra- indicates that use of dexamethasone is not associated tion of morphine decreased not only the fetal breathing with a decrease in the FHR variability (26).
movement but also the number of accelerations (31).
Other medications that influence FHR tracing have been studied (see Table 2). Pseudosinusoidal FHR pat- What findings on EFM reassure fetal status?
terns occurred in 75% of patients who received butor- The presence of FHR accelerations generally ensures that phanol during labor, but this was not associated with the fetus is not acidemic and provides reassurance of fetal adverse outcomes (27). Fetuses exposed to cocaine did status. The data relating FHR variability to clinical out- not exhibit any characteristic changes in the heart rate comes, however, are sparse. One study reported that in pattern, although they did have frequent contractions the presence of late or variable decelerations, the umbili- even when labor was unstimulated (28). Multiple regres- cal arterial pH was higher than 7 in 97% of the cases if sion analysis indicated that decreased variability associ- the FHR tracing had normal variability (32). In another ated with the use of magnesium sulfate was related to retrospective study, most cases of adverse neonatal out- early gestational age but not the serum magnesium level come demonstrated normal FHR variability (33). This (29). As determined by computer analysis of cardiotoco- study is limited because it did not consider other charac- grams, a randomized trial reported that compared with teristics of the FHR tracing, such as the presence of ac- meperidine, nalbuphine used for intrapartum analgesia celerations or decelerations. Thus, in most cases, normal decreased the likelihood of two 15-second decelerations FHR variability provides reassurance about fetal status.
ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
How is a nonreassuring EFM tracing initially
born with hypoxic–ischemic encephalopathy were 50% assessed?
The use of pulse oximetry has been suggested as a A persistently nonreassuring FHR tracing requires evalu- modality to reduce the false-positive rate of a nonreas- ation of the possible causes. Initial evaluation and treat- suring FHR tracing. A multicenter randomized clinical trial reported that among term singleton fetuses with non- • Discontinuation of any labor stimulating agent reassuring FHR patterns, the use of fetal pulse oximetry • Cervical examination to assess for umbilical cord along with electronic tracing was associated with a sig- prolapse or rapid cervical dilation or descent of the nificantly lower rate (4.5%) of cesarean delivery for pre- sumed nonreassuring tracing than the controls (10%),who were managed with FHR monitoring alone (38).
• Changing maternal position to left or right lateral However, before proceeding with emergent cesarean recumbent position, reducing compression of the delivery, most of the patients had not undergone ancillary vena cava and improving uteroplacental blood flow tests to assess fetal well-being or intrauterine resuscita- • Monitoring maternal blood pressure level for evi- tion, both of which could have decreased the need to pro- dence of hypotension, especially in those with region- ceed with cesarean delivery. Moreover, the randomized al anesthesia (if present, treatment with ephedrine or trial decreased neither the overall rate of cesarean deliv- ery nor the rate of umbilical arterial pH less than 7.
• Assessment of patient for uterine hyperstimulation Because of the uncertain benefit of pulse oximetry and by evaluating uterine contraction frequency and concerns about falsely reassuring fetal oxygenation, use of the fetal pulse oximeter in clinical practice cannot besupported at this time. Additional studies to test the effi- Are there ancillary tests that reassure fetal
cacy and safety of fetal pulse oximetry are underway.
status?
Are there methods of intrauterine resuscita-
The false-positive rate of EFM is high. There are some tion that can be used for persistently nonreas-
ancillary tests available that help to ensure fetal well- suring patterns?
being in the face of a nonreassuring FHR tracing, there-by reducing the false-positive rate of EFM.
Maternal oxygen commonly is used in cases of a persist- In the case of an EFM tracing with decreased or ently nonreassuring pattern. Unfortunately, there are no absent variability without spontaneous accelerations, an data on the efficacy or safety of this therapy. Often, the effort should be made to elicit one. A meta-analysis of 11 nonreassuring FHR patterns persist and do not respond to studies of intrapartum fetal stimulation noted that four change in position or oxygenation. In such cases, the use techniques are available to stimulate the fetus: 1) fetal of tocolytic agents has been suggested to abolish uterine scalp sampling, 2) Allis clamp scalp stimulation, 3) vibro- contractions and perhaps avoid umbilical cord compres- acoustic stimulation, and 4) digital scalp stimulation (34).
sion. A meta-analysis reported the pooled results of three Each of these tests is a reliable method to exclude acidosis randomized clinical trials that compared tocolytic ther- if accelerations are noted after stimulation. Because apy (terbutaline, hexoprenaline, or magnesium sulfate) vibroacoustic stimulation and scalp stimulation are less with untreated controls in the management of a suspect- invasive than the other two methods, they are the preferred ed nonreassuring FHR tracing (39). Compared with no methods. When there is an acceleration following stimula- treatment, tocolytic therapy more commonly improved tion, acidosis is unlikely and labor can continue.
the FHR tracing. However, there were no differences in When a nonreassuring FHR tracing persists and nei- rates of perinatal mortality, low 5-minute Apgar score, or ther spontaneous nor stimulated accelerations are pres- admission to the neonatal intensive care unit between the ent, a scalp blood sample for the determination of pH or groups (possibly because of the small sample size). Thus, lactate can be considered. However, the use of scalp pH although tocolytic therapy appears to reduce the number has decreased (35), and it may not even be available at of FHR abnormalities, there is insufficient evidence to some tertiary hospitals (36). The sensitivity and positive predictive value of a low scalp pH (defined in the study Hyperstimulation (six or more contractions in 10 min- as less than 7.21 because it is the 75th percentile) to pre- utes) or hypertonus (single contraction lasting more dict umbilical arterial pH less than 7 were 36% and 9%, than 2 minutes) in conjunction with a nonreassuring FHR respectively. More importantly, the sensitivity and posi- pattern can be successfully treated with β -adrenergic tive predictive value of a low scalp pH to identify a new- drugs (hexoprenaline or terbutaline). A retrospective study ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
OBSTETRICS & GYNECOLOGY
suggested that 98% of cases of uterine hyperstimulation The use of fetal pulse oximetry in clinical practice respond to treatment with a β-agonist (40).
When the FHR abnormality is recurrent variable decelerations, amnioinfusion to relieve umbilical cordcompression should be considered (41). A meta-analysis References
of 12 randomized trials that allocated patients to no treat- 1. Martin JA, Hamilton BE, Ventura SJ, Menacker F, Park ment or transcervical amnioinfusion noted that place- MM, Sutton PD. Births: final data for 2002. Natl Vital Stat ment of fluid in the uterine cavity significantly reduced the rate of decelerations (relative risk 0.54, 95% CI, 2. Low JA, Pickersgill H, Killen H, Derrick EJ. The predic- 0.43–0.68) and cesarean delivery for suspected fetal dis- tion and prevention of intrapartum fetal asphyxia in term tress (relative risk 0.35, 95% CI, 0.24–0.52) (42).
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Because of the lower rate of cesarean delivery, amnioin- fusion also decreased the likelihood that either the 3. Thacker SB, Stroup D, Chang M. Continuous electronic patient or the newborn will stay in the hospital more than heart rate monitoring for fetal assessment during labor.
The Cochrane Database of Systematic Reviews 2001, 3 days (42). Amnioinfusion can be done by bolus or con- Issue 2. Art. No.: CD000063. DOI: 10.1002/14651858.
tinuous infusion technique. A randomized trial compared the two techniques of amnioinfusion and concluded that 4. Electronic fetal heart rate monitoring: research guidelines both have a similar ability to relieve recurrent variable for interpretation. National Institute of Child Health and Human Development Research Planning Workshop. Am J Another common cause of nonreassuring FHR pat- Obstet Gynecol 1997;177:1385–90. (Level III) terns is maternal hypotension secondary to regional 5. Freeman RK. Problems with intrapartum fetal heart rate anesthesia. If maternal hypotension is identified and sus- monitoring interpretation and patient management. ObstetGynecol 2002;100:813–26. (Level III) pected to be secondary to regional anesthesia, treatmentwith intravenous ephedrine is warranted.
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Recommendations
7. Nelson KB, Dambrosia JM, Ting TY, Grether JK.
Uncertain value of electronic fetal monitoring in pre- and Conclusions
dicting cerebral palsy. N Engl J Med 1996,324:613–8.
(Level II-2) The following recommendations are based on
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electronic fetal heart rate monitoring versus intermittentauscultation in detecting fetal acidemia at birth. Am J ited or inconsistent scientific evidence (Level B):
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inter-observer variability in the assessment of intrapartum ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring
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Studies were reviewed and evaluated for quality accordingto the method outlined by the U.S. Preventive Services Task Intrapartum fetal heart rate monitoring. ACOG Practice Bulletin No. 62.
American College of Obstetricians and Gynecologists. Obstet Gynecol2005;105:1161–69.
Evidence obtained from at least one properly de-signed randomized controlled trial.
II-1 Evidence obtained from well-designed controlled II-2 Evidence obtained from well-designed cohort or case–control analytic studies, preferably from morethan one center or research group.
II-3 Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncon-trolled experiments also could be regarded as thistype of evidence.
Opinions of respected authorities, based on clinicalexperience, descriptive studies, or reports of expertcommittees.
Based on the highest level of evidence found in the data,recommendations are provided and graded according to thefollowing categories:Level A—Recommendations are based on good and consis-tent scientific evidence.
Level B—Recommendations are based on limited or incon-sistent scientific evidence.
Level C—Recommendations are based primarily on con-sensus and expert opinion.
ACOG Practice Bulletin No. 62 Intrapartum Fetal Heart Rate Monitoring

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