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Fetal electrocardiogram (ECG) for fetal monitoring during labour

  1. James P Neilson*

Editorial Group: Cochrane Pregnancy and Childbirth Group

Published Online: 31 MAY 2013

Assessed as up-to-date: 12 FEB 2013

DOI: 10.1002/14651858.CD000116.pub4


How to Cite

Neilson JP. Fetal electrocardiogram (ECG) for fetal monitoring during labour. Cochrane Database of Systematic Reviews 2013, Issue 5. Art. No.: CD000116. DOI: 10.1002/14651858.CD000116.pub4.

Author Information

  1. The University of Liverpool, Department of Women's and Children's Health, Liverpool, UK

*James P Neilson, Department of Women's and Children's Health, The University of Liverpool, First Floor, Liverpool Women's NHS Foundation Trust, Crown Street, Liverpool, L8 7SS, UK. jneilson@liverpool.ac.uk.

Publication History

  1. Publication Status: New search for studies and content updated (no change to conclusions)
  2. Published Online: 31 MAY 2013

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This is not the most recent version of the article. View current version (21 DEC 2015)

 
Characteristics of included studies [ordered by study ID]
Amer-Wahlin 2001

MethodsRandom allocation through computer-generated random numbers table, triggered by switching on the software in the fetal monitoring equipment.


Participants4966 women in labour at > 36 weeks with singleton pregnancies, cephalic presentation and perceived need for continuous fetal heart rate monitoring via a fetal scalp electrode - high-risk pregnancies, suspicious or abnormal cardiotocography, induced labour, oxytocin augmentation, meconium-stained amniotic fluid or epidural analgesia. The trial took place between 1998 and 2000 in 3 Swedish centres, Lund, Malmo, Gothenburg.


InterventionsCTG plus ST analysis of fetal ECG (2519 women) versus CTG alone (2477). The monitoring device was the STAN S21 (Neoventa Medical, Gothenburg) which incorporates an 'expert system' to provide advice to clinical staff. In this, it constitutes a technically more advanced system than used in the Westgate 1993 trial.


OutcomesPrimary: metabolic acidosis at birth (umbilical cord artery pH < 7.05 plus base deficit > 12 mmol/L). Secondary: operative deliveries, Apgar scores at 1 and 5 minutes, admissions to special care unit.


NotesIncomplete data available for acid-base results (2159 and 2079). The published report includes a secondary analysis performed after exclusion of babies with malformations and cases associated with trial protocol violations. The results included in this review are exclusively from the primary analysis, based on 'intention-to-treat'. An interim analysis was performed after around 1800 recruits; this revealed 'protocol violations' (failure to intervene on the basis of guidance in the research protocol) and the interim results were discussed with the clinical staff at the recruiting centres as part of a process of 're-training'. The study was co-funded by the Swedish Government Public Health Service, Neoventa Medical AB (manufacturer of the STAN device) and the Knowledge Foundation, Stockholm.

Concerns were raised about the conduct and reporting of this trial, resulting in 3 separate external reviews. The final review (Swedish Research Council 2010) was critical of the role of the originator of the STAN device role as the monitor of trial - because of conflicted interests. The report also required the re-reporting of cord gas results (these have been corrected in the review and have now been published (Amer-Wahlin 2011; Marsal 2011) but other reported outcomes were not in dispute. There was no suggestion of deliberate attempts to manipulate the data (University of Lund 2010).


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Low riskAdequate.

Ojala 2006

MethodsOpaque, consecutively numbered, sealed, envelopes containing randomisation code generated by computer programme in blocks of 100. Envelope opened at time of amniotomy.


Participants1483 women randomised; 11 exclusions; clinical data available but blood gas data missing for 36. In labour at =/> 36 weeks with singleton fetus, cephalic presentation, decision to perform amniotomy, no contraindication to scalp electrode. Sample size based on 50% reduction of umbilical artery pH < 7.10.


InterventionsCTG plus ECG waveform analysis (STAN) (733 women) versus CTG (739 women). Fetal scalp sampling for pH estimation an option in either group. Recruitment in tertiary referral hospital in Finland 2003-4.


OutcomesNeonatal acidaemia, operative delivery, need for fetal scalp sampling for pH estimation.


NotesIn 83 pregnancies, there were technical difficulties in achieving satisfactory monitoring - n = 5 in CTG group; n = 78 in the ECG group.


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Low riskA - Adequate.

Strachan 2000

MethodsRandom allocation through computer-generated random numbers table, triggered by switching on the software in the fetal monitoring equipment.


Participants957 women in labour with perceived need for continuous fetal heart rate monitoring (age > 35, maternal disease, adverse obstetric history, prematurity, suspected fetal growth restriction, antepartum haemorrhage, breech presentation, multiple pregnancy, epidural analgesia, induction or augmentation of labour, abnormal cardiotocography, meconium, previous caesarean section). Results are only available for 957 women (92%) for reasons that are unclear. The trial took place in 5 centres: Nottingham and Dundee (UK), Hong Kong, Amsterdam (Netherlands) and Singapore.


InterventionsCTG plus fetal ECG (n = 482) versus CTG alone (n = 475).


OutcomesThe trial was powered to detect (alpha 80%, beta 5%) a decrease in 'unsuspected acidaemia' (cord artery pH < 7.15) from 8.5% to 4.5%.


NotesThe data monitoring committee recommended that the trial be stopped before recruitment of the target of 1192 for reasons that are not clear from the report.


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Low riskAdequate.

Vayssiere 2007

MethodsSealed, numbered, opaque envelopes were prepared in a Research Unit. Details of randomisation are not described but there was stratification by centre (2). Allocation was by opening the next envelope.


Participants799 women in labor at 36 weeks or more, with a single fetus with cephalic presentation, and either abnormal cardiotocographic trace or thick meconium-stained amniotic fluid. Exclusions included maternal infections that contraindicated scalp electrode attachment (e.g. HIV), cardiac malformation, severely abnormal cardiotocography at the time of recruitment.


InterventionsCTG + fetal ECG (n = 399) versus CTG alone (n = 400). Scalp sampling for ph estimation was an option in both groups.


OutcomesThe trial was powered (alpha 5% beta 80%) to detect a reduction in operative deliveries for 'fetal distress' from 50% to 40%.


NotesFetal ECG was assessed by STAN S21 machines.


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Low riskAdequate.

Westerhuis 2010

MethodsA randomised clinical trial of cardiotocography plus ST-analysis of the fetal ECG (STAN®) versus cardiotocography alone for intrapartum fetal monitoring. Women randomised through a computer-generated randomisation sequence. Stratification for centre and parity (no previous vaginal delivery versus 1 or more previous vaginal deliveries). The study was performed in 9 hospitals in The Netherlands.


Participants5681 women in labour with a singleton fetus in vertex position, a gestational age 36 weeks or greater and a medical indication for electronic fetal monitoring. A medical indication is defined by either a high-risk pregnancy, induction or augmentation of labour, epidural anaesthesia, meconium-stained amniotic fluid or non-reassuring fetal heart rate.


InterventionsIntervention group: CTG and ST-analysis. Control group: CTG.


OutcomesPrimary outcome: incidence of serious metabolic acidosis defined as a pH < 7.05 and a BDecf > 12 mmol/L in the umbilical cord artery.

Secondary outcomes:

  1. incidence of serious metabolic acidosis defined as a pH < 7.05 and a BDblood > 12 mmol/L in the umbilical cord artery;
  2. instrumental delivery rate because of fetal distress, failure to progress or a combination of the two;
  3. neonatal outcome defined as Apgar scores < 4 after 1 minute and/or < 7 after 5 minutes;
  4. need for admission to neonatal medium or intensive care unit;
  5. incidence of performance of fetal blood sampling in both groups;
  6. cost-effectiveness.


Notes


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskComputer-generated; variable block size.

Allocation concealment (selection bias)Low riskWeb-based allocation.

Blinding (performance bias and detection bias)
All outcomes
High riskWomen and clinicians deliberately not blinded in this pragmatic trial. Paediatricians assessing infant outcomes were blinded.

Incomplete outcome data (attrition bias)
All outcomes
Low risk14 women excluded as they did not meet criteria for inclusion; others included in intention-to-treat analysis.

Selective reporting (reporting bias)Low risk

Other biasLow risk

Westgate 1993

MethodsRandomisation: entry to either group decided by draw of sealed, opaque envelopes once the decision to apply electrode was made.

Trial preceded by randomised study to identify the best available scalp electrode for ECG recording - single spiral electrode, used in both groups of the study. On ST + CTG group the lead collection system also required a maternal thigh electrode be applied to standardise the ECG vector.


Participants2434 pregnant women, 1215 cardiotocography alone arm, 1219 ST waveform and CTG arm. (More than 34 weeks' gestation with no gross fetal abnormality.)


InterventionsCTG plus ST analysis (n =1219) versus CTG alone (n = 1215).


OutcomesObstetric intervention (fetal blood sampling and operative delivery) and fetal outcome.


NotesOperative delivery rates separated into overall caesarean section rates and operative vaginal delivery rates not recorded in published report - information to be sought from authors.


Risk of bias

BiasAuthors' judgementSupport for judgement

Allocation concealment (selection bias)Low riskAdequate.

 
Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion

Hruban 2006Not randomised.

Janku 2006Not randomised.

Olofsson 2003Review article.

Prieto 2008Randomised trial reported as abstract only with insufficient detail to include data.

 
Characteristics of ongoing studies [ordered by study ID]
Spong 2013

Trial name or titleA randomised trial of fetal ECG ST segment and T wave analysis as an adjunct to electronic fetal heart rate monitoring (STAN)

MethodsOpen randomised trial

ParticipantsInclusion Criteria:

  • Singleton, cephalic pregnancy
  • Gestational age at least 36 weeks, 1 day
  • Cervical dilation of at least 2 cm and no more than 7 cm
  • Ruptured membranes

InterventionsOpen group: FHR monitoring with ST analysis available
Masked group: FHR monitoring with ST analysis masked

Outcomes
  • Intrapartum fetal death
  • Neonatal Death
  • Apgar score <= 3 at 5 minutes
  • Neonatal seizure
  • Cord artery pH <= 7.05 and base deficit >= 12 mmol/L
  • Intubation for ventilation at delivery
  • Presence of neonatal encephalopathy

Starting dateNovember 2010

Contact informationCatherine C Spong spongc@mail.nih.gov

Notes

 
Comparison 1. Fetal ECG plus CTG versus CTG alone

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Caesarean section6Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    1.1 ST analysis
515338Risk Ratio (M-H, Fixed, 95% CI)0.99 [0.91, 1.08]

    1.2 PR analysis
1957Risk Ratio (M-H, Fixed, 95% CI)0.79 [0.61, 1.04]

 2 Cord pH < 7.05 + base deficit > 12 mmol/L5Risk Ratio (M-H, Random, 95% CI)Subtotals only

    2.1 ST analysis
514574Risk Ratio (M-H, Random, 95% CI)0.78 [0.44, 1.37]

   2.2 PR analysis
00Risk Ratio (M-H, Random, 95% CI)0.0 [0.0, 0.0]

 3 Neonatal encephalopathy5Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    3.1 ST analysis
515302Risk Ratio (M-H, Fixed, 95% CI)0.54 [0.24, 1.25]

   3.2 PR analysis
00Risk Ratio (M-H, Fixed, 95% CI)0.0 [0.0, 0.0]

 4 Fetal blood sampling5Risk Ratio (M-H, Random, 95% CI)Subtotals only

    4.1 ST analysis
49671Risk Ratio (M-H, Random, 95% CI)0.61 [0.41, 0.91]

    4.2 PR analysis
1957Risk Ratio (M-H, Random, 95% CI)0.91 [0.69, 1.19]

 5 Operative vaginal delivery5Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    5.1 ST analysis
49671Risk Ratio (M-H, Fixed, 95% CI)0.89 [0.81, 0.98]

    5.2 PR analysis
1957Risk Ratio (M-H, Fixed, 95% CI)0.94 [0.75, 1.17]

 6 Apgar score < 7 at 5 minutes6Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    6.1 ST analysis
515302Risk Ratio (M-H, Fixed, 95% CI)0.95 [0.73, 1.24]

    6.2 PR analysis
1957Risk Ratio (M-H, Fixed, 95% CI)0.42 [0.11, 1.62]

 7 Neonatal intubation2Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    7.1 ST analysis
11436Risk Ratio (M-H, Fixed, 95% CI)0.79 [0.29, 2.10]

    7.2 PR analysis
1957Risk Ratio (M-H, Fixed, 95% CI)0.74 [0.26, 2.11]

 8 Admission neonatal special care unit6Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    8.1 ST analysis
515302Risk Ratio (M-H, Fixed, 95% CI)0.89 [0.81, 0.99]

    8.2 PR analysis
1957Risk Ratio (M-H, Fixed, 95% CI)0.77 [0.45, 1.33]

 9 Perinatal death6Risk Ratio (M-H, Fixed, 95% CI)Subtotals only

    9.1 ST analysis
515338Risk Ratio (M-H, Fixed, 95% CI)1.49 [0.53, 4.18]

    9.2 PR analysis
1957Risk Ratio (M-H, Fixed, 95% CI)2.96 [0.12, 72.39]

10 Cerebral palsy0Risk Ratio (M-H, Fixed, 95% CI)Subtotals only