Improved intrapartum surveillance with PR interval analysis of the fetal electrocardiogram: a randomized trial showing a reduction in fetal blood sampling

Effectiveness of intrapartum fetal surveillance to improve maternal and neonatal outcomes: a systematic review and network meta-analysis

BACKGROUND:

Cesarean delivery is the most common surgical procedure worldwide. Intrapartum fetal surveillance is routinely offered to improve neonatal outcomes, but the effects of different methods on the risk of emergency cesarean deliveries remains uncertain. We conducted a systematic review and network meta-analysis to evaluate the effectiveness of different types of fetal surveillance.

METHODS:

We searched MEDLINE, Embase and CENTRAL until June 1, 2020, for randomized trials evaluating any intrapartum fetal surveillance method. We performed a network meta-analysis within a frequentist framework. We assessed the quality and network inconsistency of trials. We reported primarily on intrapartum emergency cesarean deliveries and other secondary maternal and neonatal outcomes using risk ratios (RRs) and 95% confidence intervals (CIs).

RESULTS:

We included 33 trials (118 863 patients) evaluating intermittent auscultation with Pinard stethoscope/handheld Doppler (IA), cardiotocography (CTG), computerized cardiotocography (cCTG), CTG with fetal scalp lactate (CTG-lactate), CTG with fetal scalp pH analysis (CTG-FBS), CTG with fetal pulse oximetry (FPO-CTG), CTG with fetal heart electrocardiogram (CTG-STAN) and their combinations. Intermittent auscultation reduced the risk of emergency cesarean deliveries compared with other types of surveillance (IA v. CTG: RR 0.83, 95% CI 0.72–0.97; IA v. CTG-FBS: RR 0.71, 95% CI 0.63–0.80; IA v.CTG-lactate: RR 0.77, 95% CI 0.64–0.92; IA v. FPO-CTG: RR 0.75, 95% CI 0.65–0.87; IA v.FPO-CTG-FBS: RR 0.81, 95% CI 0.67–0.99; cCTG-FBS v. IA: RR 1.21, 95% CI 1.04–1.42), except STAN-CTG-FBS (RR 1.17, 95% CI 0.98–1.40). There was a similar reduction observed for emergency cesarean deliveries for fetal distress. None of the evaluated methods was associated with a reduced risk of neonatal acidemia, neonatal unit admissions, Apgar scores or perinatal death.

INTERPRETATION:

Compared with other types of fetal surveillance, intermittent auscultation seems to reduce emergency cesarean deliveries in labour without increasing adverse neonatal and maternal outcomes.

A systematic review of cardiac time intervals utilising non-invasive fetal electrocardiogram in normal fetuses

BACKGROUND

Non-invasive fetal electrocardiogram (NIFECG) is an evolving technology in fetal surveillance which is attracting increasing research interest. There is however, only limited data outlining the reference ranges for normal cardiac time intervals (CTIs). The objective of our group was to carry out a systematic review to outline normal fetal CTIs using NIFECG.

METHODS

A systematic review of peer reviewed literature was performed, searching PUBMED,Ovid MEDLINE and EMBASE. The outcomes of interest included fetal CTIs (P wave duration, PR interval, QRS duration and QT interval) and a descriptive summary of relevant studies as well. The outcomes were grouped as early pre-term (≤ 32 weeks), moderate to late pre-term (32-37 weeks) and term (37-41 weeks).

RESULTS

8 studies were identified as suitable for inclusion. Reference ranges of CTIs were generated. Both PR interval and QRS duration demonstrated a linear correlation with advancing gestation. Several studies also demonstrated a reduction in signal acquisition between 27 and 32 weeks due to the attenuation by vernix caseosa. In this group, both the P wave and T waves were difficult to detect due to signal strength and interference.

CONCLUSION

NIFECG demonstrates utility to quantify CTIs in the fetus, particularly at advanced gestations. Larger prospective studies should be directed towards establishing reliable CTIs across various gestations.

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 23 September 2015) and reference lists of retrieved studies.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

One review author independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. One review author assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

Seven trials (27,403 women) were included: six trials of ST waveform analysis (26,446 women) and one trial of PR interval analysis (957 women). The trials were generally at low risk of bias for most domains and the quality of evidence for ST waveform analysis trials was graded moderate to high. In comparison to continuous electronic fetal heart rate monitoring alone, the use of adjunctive ST waveform analysis made no obvious difference to primary outcomes: births by caesarean section (risk ratio (RR) 1.02, 95% confidence interval (CI) 0.96 to 1.08; six trials, 26,446 women; high quality evidence); 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) (average RR 0.72, 95% CI 0.43 to 1.20; six trials, 25,682 babies; moderate quality evidence); or babies with neonatal encephalopathy (RR 0.61, 95% CI 0.30 to 1.22; six trials, 26,410 babies; high quality evidence). There were, however, on average fewer fetal scalp samples taken during labour (average RR 0.61, 95% CI 0.41 to 0.91; four trials, 9671 babies; high quality evidence) although the findings were heterogeneous and there were no data from the largest trial (from the USA). There were marginally fewer operative vaginal births (RR 0.92, 95% CI 0.86 to 0.99; six trials, 26,446 women); but no obvious difference in the number of babies with low Apgar scores at five minutes or babies requiring neonatal intubation, or babies requiring admission to the special care unit (RR 0.96, 95% CI 0.89 to 1.04, six trials, 26,410 babies; high quality evidence). There was little evidence that monitoring by PR interval analysis conveyed any benefit of any sort.

AUTHORS' CONCLUSIONS

The modest benefits of fewer fetal scalp samplings during labour (in settings in which this procedure is performed) and fewer instrumental vaginal births have to be considered against the disadvantages of needing to use an internal scalp electrode, after membrane rupture, for ECG waveform recordings. We found little strong evidence that ST waveform analysis had an effect on the primary outcome measures in this systematic review.There was a lack of evidence showing that PR interval analysis improved any outcomes; and a larger future trial may possibly demonstrate beneficial effects.There is little information about the value of fetal ECG waveform monitoring in preterm fetuses in labour. Information about long-term development of the babies included in the trials would be valuable.

Fetal anesthesia and pain management for intrauterine therapy

Anesthesia provision for fetal intervention differs from most other anesthetic situations insofar as anesthesiologists must care for 2 or more patients-each with potentially conflicting requirements. The first is the mother who can readily indicate discomforts, can be monitored directly, and to whom drugs may be administered directly and easily. For the fetus (or fetuses), nociception must be assumed or inferred indirectly, monitoring is limited at best, and drug administration is complicated and often indirect. Fetal and maternal hemodynamic stability must be assured; and a plan to resuscitate the fetus, should problems occur during the procedure, must be developed.

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.

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.

Probing the fetal cardiac signal for antecedents of brain injury

Obstetric care providers and researchers have long relied on analysis of the fetal heart rate tracing for insight into the fetal neurologic status. Although a normal fetal heart rate tracing does provide reassurance of intact neurologic function, an abnormal pattern is a very poor predictor of newborn brain injury. Indeed, if the clinical end point of interest is cerebral palsy, a non-reassuring fetal heart rate tracing has a 99% false positive rate. More recent analyses of fetal heart rate variability and fetal ECG waveforms, however, hold promise for improved diagnostic accuracy.

Cesarean section for suspected fetal distress, continuous fetal heart monitoring and decision to delivery time

OBJECTIVE

To find out the efficacy of continuous fetal heart monitoring by analyzing the cases of cesarean section for nonreassuring fetal heart in labor, detected by cardiotocography (CTG) and correlating these cases with perinatal outcome. To evaluate whether a 30 minute decision to delivery (D-D) interval for emergency cesarean section influences perinatal outcome.

METHODS

This was a prospective observational study of 217 patients who underwent cesarean section at > or = 36 weeks for non-reassuring fetal heart in labor detected by CTG. The maternal demographic profile, specific types of abnormal fetal heart rate tracing and the decision to delivery time interval were noted. The adverse immediate neonatal outcomes in terms of Apgar score <7 at 5 minutes, umbilical cord thornH <7.10, neonates requiring immediate ventilation and NICU admissions were recorded. The correlation between non-reassuring fetal heart, decision to delivery interval and neonatal outcome were analyzed.

RESULTS

Out of 3148 patients delivered at > or = 36 weeks, 217 (6.8%) patients underwent cesarean section during labor primarily for non-reassuring fetal heart. The most common fetal heart abnormality was persistent bradycardia in 106 (48.8%) cases followed by late deceleration in 38 (17.5%) cases and decreased beat to beat variability in 17 (7.8%) cases. In 33 (15.2%) babies the 5 minutes Apgar score was <7 out of which 13 (5.9%) babies had cord thornH <7.10. Thirty three (15.2%) babies required NICU admission for suspected birth asphyxia. Rest 184 (84.7%) neonates were born healthy and cared for by mother. Regarding decision to delivery interval of < or =30 minutes versus >30 minutes, there was no significant difference in the incidence of Apgar score <7 at 5 minutes, cord pH <7.10 and new born babies requiring immediate ventilation. But the need for admission to NICU in the group of D-D interval < or = 30 minutes was significantly higher compared to the other group where D-D interval was >30 minutes.

CONCLUSION

Non-reassuring fetal heart rate detected by CTG did not correlate well with adverse neonatal outcome. There was no significant difference in immediate adverse neonatal outcome whether the D-D time interval was < or = 30 minutes or >30 minutes; contrary to this, NICU admission for suspected birth asphyxia in </= 30 minutes group was significantly higher.

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.

Fetal electrocardiogram (ECG) for fetal monitoring during labour

BACKGROUND

Animal and human studies have shown that fetal hypoxaemia during labour can alter the shape of the fetal electrocardiogram (ECG) waveform, notably (1) the relation of the PR to RR intervals and (2) 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

The Cochrane Pregnancy and Childbirth Group trials register was searched (September 2002).

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 reviewer, without blinding.

MAIN RESULTS

Three trials including a total of 8357 pregnant women were included. The trials were of sound methodological quality. All three trials assessed the use of the fetal ECG as an adjunct to continuous electronic fetal heart rate monitoring during labour. One study assessed PR intervals; two assessed the ST segment. The use of ST waveform analysis (7400 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) 0.44, 95% confidence interval (CI) 0.26 to 0.75, data from 6672 babies). This was achieved along with fewer fetal scalp samples during labour (RR 0.86, 95% CI 0.76 to 0.98) and fewer operative deliveries (RR 0.89, 95% CI 0.82 to 0.97). Apart from a trend (that did not achieve statistical significance) towards fewer operative deliveries (RR 0.87, 95% CI 0.76 to 1.01), there was little evidence that monitoring by PR interval analysis conveyed any benefit. This may reflect limitations of the technique or, alternatively, the smaller numbers available for analysis from the single trial (957 women).

REVIEWER'S CONCLUSIONS

These findings support the use of fetal ST waveform analysis when a decision has been made to undertake continuous electronic fetal heart rate monitoring during labour. However, in most labours, technically satisfactory cardiotocographic traces can be obtained by external ultrasound monitors which are less invasive than internal scalp electrodes (which are required for electrocardiographic (ECG) analysis). A better approach might be to restrict fetal ST waveform analysis to those fetuses demonstrating disquieting features on cardiotocography.

Use of tissue velocity imaging in the diagnosis of fetal cardiac arrhythmias

BACKGROUND

Precise diagnosis of cardiac arrhythmias in the fetus is crucial for a managed therapeutic approach. However, many technical, positional, and gestational age-related limitations may render conventional methods, such as M-mode and Doppler flow methodologies, or newer techniques, such as fetal electrocardiography or magnetocardiography, difficult to apply, or these techniques may be unsuitable for the diagnosis of fetal arrhythmias.

METHODS AND RESULTS

In this prospective study, we describe a novel method based on raw scan-line tissue velocity data acquisition and analysis. The raw data are available from high-frame-rate 2D tissue velocity images and allow simultaneous sampling of right and left atrial and ventricular wall velocities to yield precise temporal analysis of atrial and ventricular events. Using this timing data, a ladder diagram-like "fetal kinetocardiogram" was developed to diagram and diagnose arrhythmias and to provide true intervals. This technique was feasible and fast, yielding diagnostic results in all 31 fetuses from 18 to 38 weeks of gestation. Analysis of various supraventricular and ventricular arrhythmias was readily obtained, including arrhythmias that conventional methods fail to diagnose.

CONCLUSIONS

The fetal kinetocardiogram opens a new window to aid in the diagnosis and understanding of fetal arrhythmias, and it provides a tool for studying the action of antiarrhythmic drugs and their effects on electrophysiological conduction in the fetal heart.

Intrapartum fetal surveillance

Intrapartum hypoxia was thought to contribute to the incidence of cerebral palsy, seizures and mental retardation. Electronic fetal monitoring was expected to prevent or reduce this incidence. Electronic fetal monitoring has a high false positive rate and fetal blood sampling, which is an invasive procedure, only allows an intermittent assessment. Efforts are being made to improve fetal heart rate analysis and clinical management. Fetal pulse oximetry, fetal electrocardiogram waveform analysis and the intermittent measurement of lactate levels by fetal blood sampling may become established as an adjunct to electronic fetal monitoring.

The fetal electrocardiogram: relationship with acidemia at delivery

OBJECTIVE

This study was undertaken to analyze the relationship between the fetal electrocardiogram and arterial pH and base excess at delivery.

STUDY DESIGN

In the labor wards of three teaching hospitals a retrospective observational study was conducted on fetal monitor recordings of 679 women for whom there was an indication for continuous fetal monitoring during labor. These women had been recruited as part of either observational studies or a prospective randomized trial related to the Nottingham fetal electrocardiographic project. Fetal heart and uterine contraction data were obtained with the Nottingham fetal electrocardiographic analyzer. Morphologic and time interval analyses of the fetal electrocardiogram were performed. Evaluation was carried out for the last half hour before delivery. Main outcome measures were umbilical arterial pH and base excess at delivery.

RESULTS

The study demonstrated a relationship between time interval analysis of the fetal electrocardiogram and a low umbilical arterial pH and base excess at delivery. Analysis of the morphologic characteristics of the fetal electrocardiogram (ST segment and T-wave height) showed no significant relationship.

CONCLUSIONS

Time interval analysis of the fetal electrocardiogram during labor is related to relative acidemia at delivery.

The PR interval-fetal heart rate relationship during repetitive umbilical cord occlusions in immature fetal sheep

OBJECTIVE

To evaluate the relationship of the PR interval and fetal heart rate during repetitive umbilical cord occlusions in immature sheep fetuses.

STUDY DESIGN

In seven chronically cannulated immature sheep fetuses [gestational age 90.6 days (mean)], we analyzed continuous fetal electrocardiogram recordings during repetitive cord occlusions for 2 out of every 5 min until fetal mean arterial pressure dropped to 50% of baseline value. PR interval-fetal heart rate correlation coefficients (Pearson) was measured on consecutive blocks of 2.5 min. R-values of the baseline and the repetitive occlusion period were compared by Fisher's exact test.

RESULTS

Repetitive cord occlusions resulted in acidosis and hypotension. Two fetuses died at the end of the repetitive occlusion period. Four out of seven fetuses showed a significant change from a negative relationship between the PR interval and fetal heart rate during baseline to a predominantly positive relationship during the repetitive occlusion period.

CONCLUSION

In immature fetal sheep, a change from a negative relationship between the PR interval and fetal heart rate to a predominantly positive relationship between the PR interval and fetal heart rate was observed in four out of seven fetuses following the initiation of repetitive umbilical cord occlusions.

Cardiotocography only versus cardiotocography plus PR-interval analysis in intrapartum surveillance: a randomised, multicentre trial. FECG Study Group

BACKGROUND

There is a need to improve the sensitivity and specificity of fetal monitoring during labour. We compared the gold standard, cardiotocography, with cardiotocography plus time-interval analysis of the fetal electrocardiogram in fetal surveillance. The aim was to find out whether time-interval analysis decreased the need for operative intervention due to fetal distress.

METHODS

We did a randomised, prospective trial in five hospitals in the UK, Hong Kong, the Netherlands, and Singapore. 1038 women undergoing high-risk labours were randomly assigned fetal monitoring by cardiotocography alone, or cardiotocography plus fetal electrocardiography (ECG). Outcomes measured were rates of operative intervention, and neonatal outcome. Analysis was by intention to treat.

FINDINGS

515 women were assigned management by cardiotocography, and 523 cardiotocography plus fetal ECG. There was a trend towards fewer operative interventions for presumed fetal distress in the time-interval analysis plus cardiotocography group (63 [13%] vs 78 [16%]), but this was not significant (relative risk 0.80 [95% CI 0.59-1.08], p=0.17). There was no significant difference between groups in the proportion of babies who had an umbilical arterial pH of 7.15 or less (51 [11%] vs 49 [11%]; 1.01 [0.7-1.47]), or in the frequency of unsuspected acidaemia (42 [9%] vs 35 [8%]; 1.17 [0.76-1.79]).

INTERPRETATION

The addition of time-interval analysis of the fetal electrocardiogram during labour did not show a significant benefit in decreasing operative intervention. There was no significant difference in neonatal outcome.

Fetal distress

The term 'fetal distress' should be replaced by 'suspected fetal compromise' because the diagnosis of 'fetal distress' is often unproven. Cardiotocography remains the cornerstone of making the diagnosis, but as a test it is renowned for its high sensitivity and low specificity. It has reduced intrapartum fetal mortality but not long-term neonatal morbidity or the incidence of cerebral palsy. There is no doubt that when obvious signs of fetal compromise, such as late decelerations in the presence of intrauterine growth retardation and oligohydramnios, are present, the diagnosis of fetal compromise is relatively simple. Often, however, the subtle signs of fetal compromise are missed; these are a change in the grade of meconium in the amniotic fluid, a rising base-line fetal heart rate, the absence of accelerations, the presence of 'atypical' variable decelerations or a combination of the above. To date, there is no test available to replace the cardiotocograph, although fetal pulse oximetry is the most promising adjunctive test. Above all, no test result obtained in isolation must detract from the whole clinical picture.

Improving intrapartum surveillance: an individualised T/QRS ratio?

OBJECTIVES

To test the T/QRS ratio of the fetal electrocardiogram for normal distribution and assess the potential value of an individualised T/QRS ratio threshold to depict abnormality in the detection of fetal compromise during labour.

STUDY DESIGN

A retrospective analysis of twenty intrapartum fetal electrocardiogram recordings obtained on the labour ward of the Queen's Medical Centre, Nottingham.

RESULTS

In two of the twenty cases the T/QRS ratio was normally distributed. An increase in the T/QRS ratio over the 97.5th and 99.5th centile for 2 consecutive minutes, calculated on an individual basis, would appear to discriminate best between biochemically compromised and non-compromised fetuses. In no case was the T/QRS ratio seen to exceed 0.25 for periods previously described to be related to poor outcome.

CONCLUSION

T/QRS ratio changes with individually calculated criteria for abnormality may be of benefit in the detection of fetal compromise but the effect on the intervention rate remains to be established. The use of an absolute threshold for T/QRS ratio abnormality which is based on the assumption of a normal distribution needs to be viewed with caution.

The new obstetrics: its integration into neonatal clinical practise, teaching and research

Most neonatologists have not yet incorporated into their teaching, clinical service and research the advances in high risk obstetrics particularly as it relates to fetal surveillance. This brief review emphasizes some of the "new obstetrics" from the viewpoint of perinatal medicine, particularly in terms of neonatal teaching and the design of future neonatal research. The information that can be obtained about an infant prenatally by the use of ultrasound. power doppler, computerized fetal heart rate monitoring, cordocentesis, etc is extensive and yet, has rarely been utilized in the design of neonatal research protocols. It is becoming imperative that the "new obstetrics" be recognized and utilized in modern neonatal thinking if a truly "perinatal medicine" is to be practised.

Computerised estimation of the baseline fetal heart rate in labour: the low frequency line

OBJECTIVE

To develop and evaluate a computerised algorithm for the estimation of the fetal heart rate baseline (low frequency line) during labour.

DESIGN

Retrospective observational study.

METHODS

Fetal heart rate signals were obtained from women in labour using the Nottingham fetal ECG monitor. The computerised algorithm for the baseline estimation was developed for intrapartum applications and is based on averaging modal fetal heart rate values. Evaluation was carried out on sixty cardiotocographic recordings by 12 experts and by the computer. These estimates were compared with those obtained from the computerised system using paired differences and intraclass correlation.

RESULTS

The study showed that it is possible to produce a low frequency line from data obtained from intrapartum records. The system could not estimate the low frequency line in four records, whereas experts were also unable to estimate between one and seven tracings. The 95% CI for the paired differences between computer and experts was -12 to 15 bpm, whereas between the experts this was -10 to 10. With the exception of one expert, there was a high concordance between experts and between computer and experts (intraclass correlation > 0.9).

CONCLUSIONS

The performance of this computerised algorithm cannot be distinguished from that of experienced clinicians. There were no significant differences between baseline values obtained by the computerised algorithm and those by the clinicians.

Changes in the PR interval--fetal heart rate relationship of the electrocardiogram during fetal compromise in chronically instrumented sheep

OBJECTIVES

The evaluation of the changes in the relationship of the PR interval and fetal heart rate during prolonged fetal compromise in sheep at levels of acidosis comparable to those seen during human fetal compromise and to see whether these changes are potentially of use in the detection of fetal distress.

STUDY DESIGN

A retrospective analysis of continuous fetal electrocardiogram recordings during graded fetal hypoxemia in 20 chronically cannulated fetal sheep was performed. Baseline recordings during normoxemia were compared with recordings during hypoxemia by use of Fisher's exact test and the Student t test.

RESULTS

Sixteen of the 20 cases could be used for final analysis. Twelve showed a statistically significant change from a predominantly negative relationship between the PR interval and the fetal heart rate during normoxemia to a predominantly positive relationship during hypoxemia. Two cases showed an obvious trend in the same direction, which was statistically not significant. In two other cases no change in the relationship was observed.

CONCLUSION

A changing relation between the PR interval and the fetal heart rate is of potential use in the detection of fetal compromise.

The fetal electrocardiogram

Advances in microprocessing technology have made fetal ECG analysis a feasible adjunct to fetal surveillance. Time interval and morphology changes of the FECG occur during fetal hypoxia. The use of these changes to detect a fetus at risk of intrapartum asphyxia awaits validation in terms of both future and ongoing clinical trials. Recognition of FECG changes during decelerations may improve the sensitivity of EFM. Antepartum FECG analysis has potential for the detection of a number of pathological fetal conditions, including intrauterine growth retardation, but remains hampered by low signal-to-noise ratios, rendering successful signal acquisition unreliable.