Cardiotocography Plus ST Analysis of Fetal Electrocardiogram Compared With Cardiotocography Only for Intrapartum Monitoring: A Randomized Controlled Trial

Scientific and clinical evidence for the use of fetal ECG ST segment analysis (STAN)

Fetal electrocardiogram waveform analysis has been studied for many decades, but it is only in the last 20 years that computerization has made real-time analysis practical for clinical use. Changes in the ST segment have been shown to correlate with fetal condition, in particular with acid-base status. Meta-analysis of randomized trials (five in total, four using the computerized system) has shown that use of computerized ST segment analysis (STAN) reduces the need for fetal blood sampling by about 40%. However, although there are trends to lower rates of low Apgar scores and acidosis, the differences are not statistically significant. There is no effect on cesarean section rates. Disadvantages include the need for amniotic membranes to be ruptured so that a fetal scalp electrode can be applied, and the need for STAN values to be interpreted in conjunction with detailed fetal heart rate pattern analysis.

Fetal ECG extraction from abdominal signals: a review on suppression of fundamental power line interference component and its harmonics

Interference of power line (PLI) (fundamental frequency and its harmonics) is usually present in biopotential measurements. Despite all countermeasures, the PLI still corrupts physiological signals, for example, electromyograms (EMG), electroencephalograms (EEG), and electrocardiograms (ECG). When analyzing the fetal ECG (fECG) recorded on the maternal abdomen, the PLI represents a particular strong noise component, being sometimes 10 times greater than the fECG signal, and thus impairing the extraction of any useful information regarding the fetal health state. Many signal processing methods for cancelling the PLI from biopotentials are available in the literature. In this review study, six different principles are analyzed and discussed, and their performance is evaluated on simulated data (three different scenarios), based on five quantitative performance indices.

A risk stratification model to predict adverse neonatal outcome in labor

OBJECTIVE

The development and evaluation of a labor risk model consisting of a combination of antepartum risk factors and intrapartum fetal heart rate (FHR) characteristics that can reliably identify those infants at risk for adverse neonatal outcome in labor.

STUDY DESIGN

A nested case-control study of term singleton deliveries at the nine hospitals between March 2007 and December 2009. Eligibility criteria included: gestational age ≥ 37.0 weeks; singleton pregnancy; documented continuous FHR monitoring for ≥ 2 h before delivery; assessment of FHR tracing at least every 20 min; and, available maternal and neonatal outcomes. Adverse neonatal outcome was defined as nonanomalous infants admitted to the newborn intensive care unit with either a 5 minute Apgar score <7 or an umbilical artery pH<7.1. Initial risk score was determined using data available at 1 h after admission. Patients with an initial risk score between 7 and 15 were considered high risk. Intrapartum risk scores were then created for these patients using FHR tracing data and labor characteristics.

RESULT

A total of 51 244 patients were identified meeting study criteria. Of the antepartum variables evaluated (n=31), 10 were associated with an adverse outcome. The high-risk group made up 28% of the population and accounted for 59.8% of the adverse outcomes. Intrapartum characteristics were then evaluated in this high-risk group. Intrapartum evaluation identified the highest risk group with a C/S rate of 40% and adverse outcome rate of 11.3%.

CONCLUSION

Incorporation of maternal and antepartum risk factors with FHR analysis can improve the ability to identify the fetus at risk in labor.

Fetal electrocardiogram (ECG) for fetal monitoring during labour

BACKGROUND

Hypoxaemia during labour can alter the shape of the fetal electrocardiogram (ECG) waveform, notably the relation of the PR to RR intervals, and elevation or depression of the ST segment. Technical systems have therefore been developed to monitor the fetal ECG during labour as an adjunct to continuous electronic fetal heart rate monitoring with the aim of improving fetal outcome and minimising unnecessary obstetric interference.

OBJECTIVES

To compare the effects of analysis of fetal ECG waveforms during labour with alternative methods of fetal monitoring.

SEARCH METHODS

The Cochrane Pregnancy and Childbirth Group's Trials Register (latest search 12 February 2013).

SELECTION CRITERIA

Randomised trials comparing fetal ECG waveform analysis with alternative methods of fetal monitoring during labour.

DATA COLLECTION AND ANALYSIS

Trial quality assessment and data extraction were performed by one review author, without blinding.

MAIN RESULTS

Six trials (16,295 women) were included: five trials of ST waveform analysis (15,338 women) and one trial of PR interval analysis (957 women). In comparison to continuous electronic fetal heart rate monitoring alone, the use of adjunctive ST waveform analysis made no significant difference to primary outcomes: births by caesarean section (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.91 to 1.08), the number of babies with severe metabolic acidosis at birth (cord arterial pH less than 7.05 and base deficit greater than 12 mmol/L) (RR 0.78, 95% CI 0.44 to 1.37, data from 14,574 babies), or babies with neonatal encephalopathy (RR 0.54, 95% CI 0.24 to 1.25). There were, however, on average fewer fetal scalp samples taken during labour (RR 0.61, 95% CI 0.41 to 0.91) although the findings were heterogeneous; there were fewer operative vaginal deliveries (RR 0.89, 95% CI 0.81 to 0.98) and admissions to special care unit (RR 0.89, 95% CI 0.81 to 0.99); there was no statistically significant difference in the number of babies with low Apgar scores at five minutes or babies requiring neonatal intubation. There was little evidence that monitoring by PR interval analysis conveyed any benefit.

AUTHORS' CONCLUSIONS

These findings provide some modest support for the use of fetal ST waveform analysis when a decision has been made to undertake continuous electronic fetal heart rate monitoring during labour. However, the advantages need to be considered along with the disadvantages of needing to use an internal scalp electrode, after membrane rupture, for ECG waveform recordings.

Managing the primary cesarean delivery rate

One third of deliveries in the United States are by cesarean, a rate that far exceeds that recommended by professional organizations and experts. A dominant reason for the high overall cesarean rate is the rising primary cesarean rate. The high primary cesarean rate results from multiple factors, both clinical and nonclinical. This review outlines proposed interventions to lower the primary cesarean rate. We focus on those implementable at a facility level and would likely yield immediate results, including aligning provider incentives for vaginal birth, limiting elective induction of labor, and improving labor management of dystocia and abnormal fetal heart rate tracings.

A clinical prediction model to assess the risk of operative delivery

OBJECTIVE

To predict instrumental vaginal delivery or caesarean section for suspected fetal distress or failure to progress.

DESIGN

Secondary analysis of a randomised trial.

SETTING

Three academic and six non-academic teaching hospitals in the Netherlands.

POPULATION

5667 labouring women with a singleton term pregnancy in cephalic presentation.

METHODS

We developed multinomial prediction models to assess the risk of operative delivery using both antepartum (model 1) and antepartum plus intrapartum characteristics (model 2). The models were validated by bootstrapping techniques and adjusted for overfitting. Predictive performance was assessed by calibration and discrimination (area under the receiver operating characteristic), and easy-to-use nomograms were developed.

MAIN OUTCOME MEASURES

Incidence of instrumental vaginal delivery or caesarean section for fetal distress or failure to progress with respect to a spontaneous vaginal delivery (reference).

RESULTS

  375 (6.6%) and 212 (3.6%) women had an instrumental vaginal delivery or caesarean section due to fetal distress, and 433 (7.6%) and 571 (10.1%) due to failure to progress, respectively. Predictors were age, parity, previous caesarean section, diabetes, gestational age, gender, estimated birthweight (model 1) and induction of labour, oxytocin augmentation, intrapartum fever, prolonged rupture of membranes, meconium stained amniotic fluid, epidural anaesthesia, and use of ST-analysis (model 2). Both models showed excellent calibration and the receiver operating characteristics areas were 0.70-0.78 and 0.73-0.81, respectively.

CONCLUSION

  In Dutch women with a singleton term pregnancy in cephalic presentation, antepartum and intrapartum characteristics can assist in the prediction of the need for an instrumental vaginal delivery or caesarean section for fetal distress or failure to progress.

Fetal electrocardiogram (ECG) for fetal monitoring during labour

BACKGROUND

Hypoxaemia during labour can alter the shape of the fetal electrocardiogram (ECG) waveform, notably the relation of the PR to RR intervals, and elevation or depression of the ST segment. Technical systems have therefore been developed to monitor the fetal ECG during labour as an adjunct to continuous electronic fetal heart rate monitoring with the aim of improving fetal outcome and minimising unnecessary obstetric interference.

OBJECTIVES

To compare the effects of analysis of fetal ECG waveforms during labour with alternative methods of fetal monitoring.

SEARCH METHODS

The Cochrane Pregnancy and Childbirth Group's Trials Register (28 February 2012).

SELECTION CRITERIA

Randomised trials comparing fetal ECG waveform analysis with alternative methods of fetal monitoring during labour.

DATA COLLECTION AND ANALYSIS

Trial quality assessment and data extraction were performed by one review author, without blinding.

MAIN RESULTS

Six trials (16,295 women) were included: five trials of ST waveform analysis (15,338 women) and one trial of PR interval analysis (957 women). In comparison to continuous electronic fetal heart rate monitoring alone, the use of adjunctive ST waveform analysis made no significant difference to primary outcomes: births by caesarean section (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.91 to 1.08), the number of babies with severe metabolic acidosis at birth (cord arterial pH less than 7.05 and base deficit greater than 12 mmol/L) (RR 0.78, 95% CI 0.44 to 1.37, data from 14,574 babies), or babies with neonatal encephalopathy (RR 0.54, 95% CI 0.24 to 1.25). There were, however, on average fewer fetal scalp samples taken during labour (RR 0.61, 95% CI 0.41 to 0.91) although the findings were heterogeneous; there were fewer operative vaginal deliveries (RR 0.90, 95% CI 0.81 to 0.98) and admissions to special care unit (RR 0.89, 95% CI 0.81 to 0.99); there was no statistically significant difference in the number of babies with low Apgar scores at five minutes or babies requiring neonatal intubation. There was little evidence that monitoring by PR interval analysis conveyed any benefit.

AUTHORS' CONCLUSIONS

These findings provide some modest support for the use of fetal ST waveform analysis when a decision has been made to undertake continuous electronic fetal heart rate monitoring during labour. However, the advantages need to be considered along with the disadvantages of needing to use an internal scalp electrode, after membrane rupture, for ECG waveform recordings.

Cost-effectiveness of cardiotocography plus ST analysis of the fetal electrocardiogram compared with cardiotocography only

OBJECTIVE

To assess the cost-effectiveness of addition of ST analysis of the fetal electrocardiogram (ECG; STAN) to cardiotocography (CTG) for fetal surveillance during labor compared with CTG only.

DESIGN

Cost-effectiveness analysis based on a randomized clinical trial on ST analysis of the fetal ECG.

SETTING

Obstetric departments of three academic and six general hospitals in The Netherlands. Population. Laboring women with a singleton high-risk pregnancy, a fetus in cephalic presentation, a gestational age >36 weeks and an indication for internal electronic fetal monitoring.

METHODS

A trial-based cost-effectiveness analysis was performed from a health-care provider perspective.

MAIN OUTCOME MEASURES

Primary health outcome was the incidence of metabolic acidosis measured in the umbilical artery. Direct medical costs were estimated from start of labor to childbirth. Cost-effectiveness was expressed as costs to prevent one case of metabolic acidosis.

RESULTS

The incidence of metabolic acidosis was 0.7% in the ST-analysis group and 1.0% in the CTG-only group (relative risk 0.70; 95% confidence interval 0.38-1.28). Per delivery, the mean costs per patient of CTG plus ST analysis (n= 2 827) were €1,345 vs. €1,316 for CTG only (n= 2 840), with a mean difference of €29 (95% confidence interval -€9 to €77) until childbirth. The incremental costs of ST analysis to prevent one case of metabolic acidosis were €9 667.

CONCLUSIONS

The additional costs of monitoring by ST analysis of the fetal ECG are very limited when compared with monitoring by CTG only and very low compared with the total costs of delivery.

Normalized spectral power of fetal heart rate variability is associated with fetal scalp blood pH

BACKGROUND

Spectral power of fetal heart rate variability is related to fetal condition. Previous studies found an increased normalized low frequency power in case of severe fetal acidosis.

AIMS

To analyze whether absolute or normalized low or high frequency power of fetal heart rate variability is associated with fetal scalp blood pH.

STUDY DESIGN

Prospective cohort study, performed in an obstetric unit of a tertiary care teaching hospital.

SUBJECTS

Consecutive singleton term fetuses in cephalic presentation that underwent one or more scalp blood samples, monitored during labour using ST-analysis of the fetal electrocardiogram. Ten-minute continuous beat-to-beat fetal heart rate segments, preceding the scalp blood measurement were used.

OUTCOME MEASURES

Absolute and normalized spectral power in the low frequency band (0.04-0.15 Hz) and in the high frequency band (0.4-1.5 Hz).

RESULTS

In total 39 fetal blood samples from 30 patients were studied. We found that normalized low frequency and normalized high frequency power of fetal heart rate variability is associated with fetal scalp blood pH. The estimated ß of normalized low frequency power was -0.37 (95% confidence interval -0.68 to -0.06) and the relative risk was 0.69 (95% confidence interval 0.51-0.94). The estimated ß of normalized high frequency power was 0.33 (95% confidence interval 0.01-0.65) and the relative risk was 1.39 (95% confidence interval 1.01-1.92).

CONCLUSIONS

Normalized low and normalized high frequency power of fetal heart rate variability is associated with fetal scalp blood pH.

ST segment analysis as an adjunct to electronic fetal monitoring, Part I: background, physiology, and interpretation

Fetal electrocardiogram (ECG) ST segment analysis (STAN) was approved in 2005 in the United States as an adjunct to electronic fetal heart rate monitoring to determine whether obstetrical intervention is warranted when there is an increased risk for developing metabolic acidosis. STAN has utility in the reduction of fetal acidosis at birth, decreased need for fetal scalp blood sampling during labor, and decreased need for operative vaginal delivery and emergency cesarean delivery for fetal indications. This article discusses specific fetal ECG changes and their significance and the use of the STAN system.

ST segment analysis (STAN) as an adjunct to electronic fetal monitoring, Part II: clinical studies and future directions

The Part 1 article focused on the physiology and general system for interpretation of ST segment analysis (STAN) systems. This article focuses on prior clinical studies of STAN and future research directions.

[Cerebral palsy and perinatal asphyxia (II--Medicolegal implications and prevention)]

Obstetric litigation is a growing problem in developed countries and its escalating cost together with increasing medical insurance premiums is a major concern for maternity service providers, leading to obstetric practice cessation by many practitioners. Fifty-four to 74 % of claims are based on cardiotocographic (CTG) abnormalities and their interpretation followed by inappropriate or delayed reactions. A critical analysis is performed about the nine criteria identified by the American College of Obstetricians and Gynecologists and the American Academy of Pediatrics in their task force on Neonatal Encephalopathy and Cerebral Palsy: four essential criteria defining neonatal asphyxia and five other suggesting an acute intrapartum event sufficient to cause cerebral palsy in term newborns. The importance of placental histologic examination is emphasized in order to confirm sudden catastrophic events occurring before or during labor or to detect occult thrombotic processes affecting the fetal circulation, patterns of decreased placenta reserve and adaptative responses to chronic hypoxia. It may also exclude intrapartum hypoxia by revealing some histologic patterns typical of acute chorioamnionitis and fetal inflammatory response or compatible with metabolic diseases. Magnetic resonance imaging (MRI) of the infant's damaged brain is very contributive to elucidate the mechanism and timing of asphyxia in conjunction with the clinical picture, by locating cerebral injuries predominantly in white or grey matter. Intrapartum asphyxia is sometimes preventable by delivering weak fetuses by cesarean sections before birth, by avoiding some "sentinel" events, and essentially by responding appropriately to CTG anomalies and performing an efficient neonatal resuscitation. During litigation procedures, it is necessary to have access to a readable CTG, a well-documented partogram, a complete analysis of umbilical cord gases, a placental pathology and an extensive clinical work-up of the newborn infant including cerebral MRI. Malpractice litigation in obstetric care can be reduced by permanent CTG education, respect of national CTG guidelines, use of adjuncts such as fetal blood sampling for pH or lactates, regular review of adverse events in Clinical Risk Management (CRM) groups and periodic audits about low arterial cord pH in newborns, admission to neonatal unit, the need for assisted ventilation and the decision-to-delivery interval for emergency operative deliveries. Considering the fast occurrence of fetal cerebral hypoxic injuries, and thus despite an adequate management, many intrapartum asphyxias will not be preventable. Conversely, well-documented hypoxic-ischemic brain insults during the antenatal period do not automatically exclude intrapartum suboptimal obstetric care.

ST analysis of fetal electrocardiography in labor

Since its introduction more than 40 years ago, electronic fetal monitoring has become widely used for intrapartum surveillance to determine fetal wellbeing in labor. Although fetal hypoxia and acidosis are reflected in changes in fetal heart rate, there is no evidence that cardiotocography has been effective in reducing neonatal morbidity related to fetal distress occurring during labor. Indeed the specificity of this tool is poor and in many instances the incorporation of electronic fetal monitoring into intrapartum care has merely led to an increase in medical intervention rather than an improvement in neonatal outcome. Fetal electrocardiography (ECG) analysis provides an additional method for assessing the response of the fetus to hypoxia and in particular to the development of metabolic acidosis. ST changes in the fetal ECG can be quantified with computational analysis, reducing subjective interpretation that has been problematic with traditional electronic fetal monitoring. Formal algorithms indicating appropriate points for intervention in labor have been designed. The fetal ECG has been shown to be a useful adjunct to traditional electronic fetal monitoring in several randomized controlled trials with evidence of reduced rates of neonatal encephalopathy and reduced rates of obstetric intervention.

Fetal electrocardiogram (ECG) for fetal monitoring during labour

BACKGROUND

Hypoxaemia during labour can alter the shape of the fetal electrocardiogram (ECG) waveform, notably the relation of the PR to RR intervals, and elevation or depression of the ST segment. Technical systems have therefore been developed to monitor the fetal ECG during labour as an adjunct to continuous electronic fetal heart rate monitoring with the aim of improving fetal outcome and minimising unnecessary obstetric interference.

OBJECTIVES

To compare the effects of analysis of fetal ECG waveforms during labour with alternative methods of fetal monitoring.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2006).

SELECTION CRITERIA

Randomised trials comparing fetal ECG waveform analysis with alternative methods of fetal monitoring during labour.

DATA COLLECTION AND ANALYSIS

Trial quality assessment and data extraction were performed by the review author, without blinding.

MAIN RESULTS

Four trials including a total of 9829 women were included. In comparison to continuous electronic fetal heart rate monitoring alone, the use of adjunctive ST waveform analysis (three trials, 8872 women) was associated with fewer babies with severe metabolic acidosis at birth (cord pH less than 7.05 and base deficit greater than 12 mmol/L) (relative risk (RR) 0.64, 95% confidence interval (CI) 0.41 to 1.00, data from 8108 babies), fewer babies with neonatal encephalopathy (three trials, RR 0.33, 95% CI 0.11 to 0.95) although the absolute number of babies with encephalopathy was low (n = 17), fewer fetal scalp samples during labour (three trials, RR 0.76, 95% CI 0.67 to 0.86) and fewer operative vaginal deliveries (three trials, RR 0.87, 95% CI 0.78 to 0.96). There was no statistically significant difference in caesarean section (three trials, RR 0.97, 95% CI 0.84 to 1.11), Apgar score less than seven at five minutes (three trials, RR 0.80, 95% CI 0.56 to 1.14), or admissions to special care unit (three trials, RR 0.90, 95% CI 0.75 to 1.08). Apart from a trend towards fewer operative deliveries (one trial, RR 0.87, 95% CI 0.76 to 1.01), there was little evidence that monitoring by PR interval analysis conveyed any benefit.

AUTHORS' CONCLUSIONS

These findings provide some support for the use of fetal ST waveform analysis when a decision has been made to undertake continuous electronic fetal heart rate monitoring during labour. However, the advantages need to be considered along with the disadvantages of needing to use an internal scalp electrode, after membrane rupture, for ECG waveform recordings.