Continuous cardiotocography (CTG) as a form of electronic monitoring (EFM) for fetal assessment during labour

With the exception of reduction in the incidence of neonatal seizures, there were no short- or long-term benefits of routine continuous electronic fetal monitoring. The use of electronic fetal monitoring was associated with significant increases in the rates of caesarean section and assisted vaginal delivery.

RHL Commentary by Nardin JM

1. EVIDENCE SUMMARY

This Cochrane systematic review (1) evaluated the effectiveness and safety of continuous cardiotocography (CTG) (defined as an attempt to produce a continuous and simultaneous hard-copy recording of the fetal heart rate and uterine contractions in real-time throughout the woman’s labour for monitoring fetal well being) by comparing continuous CTG with: (i) no fetal monitoring; (ii) intermittent auscultation (IA) of the fetal heart rate with Pinard stethoscope or hand-held Doppler ultrasound device; and (iii) intermittent CTG.

An extensive and appropriate literature search, based on the strategy used by the Pregnancy and Childbirth Group of the Cochrane Collaboration was performed. The outcome measures proposed by the authors are those considered to be of major importance in evaluating electronic monitoring for fetal assessment. The methodology used for data extraction, analysis and presentation is sound.

A total of 12 studies involving 37 615 women were included in the review. Eleven of these studies compared continuous CTG with intermittent auscultation; six used complementary fetal blood sampling. One trial compared continuous CTG with intermittent CTG, in which fetal blood sampling was made available for both groups.

The authors included both randomized and quasi-randomized trials in the review, which caused methodological diversity or heterogeneity in the data available for the review. Three of the trials included only low-risk women, five recruited only high-risk women, while the other four evaluated women with mixed risk. Four of the included trials had inadequate allocation concealment, accounting for a total of 17 235 women, equivalent to half of the total sample size, which may have influenced the overall results. However, to deal with this problem, the authors performed a subgroup analysis based on methodological quality.

Two methodological issues regarding the current update of the review need to be mentioned. First, the main difference to the previous version(2) is the inclusion of an alternate allocation trial that contributes 14 618 low-risk women to the continuous CTG versus IA comparison (3); and second, the data from the 3-arm trial comparing continuous CTG with or without fetal scalp sample (4) were handled using an arbitrary division of the number of controls to avoid double-counting when comparing women in this group with both experimental groups. These data should also be interpreted cautiously since controls were divided into two non-randomized groups, which could weaken the statistical power and quality of the original trial.

1.1 Continuous versus intermittent CTG

Based on one trial which included 4044 women at low to moderate risk for complications, no significant differences were found between continuous CTG and intermittent CTG (5).. However, a trend favourable to intermittent CTG could be observed for most of the outcomes evaluated in the review (comparison 05), including caesarean section [relative risk (RR) 1.29, 95% confidence interval (CI) 0.84-1.97], instrumental vaginal birth (RR 1.16, 95% CI 0.92-1.46), Apgar score less than seven at five minutes (RR 2.65, 95% CI 0.70-9.97) and admission to Neonatal Intensive Care Unit (NICU) (RR 1.34, 95% CI 0.91-1.98).

1.2 Continuous CTG versus intermittent auscultation

Of the eleven trials in this comparison only two had adequate allocation concealment (13 314 women), five were unclear (3032 women), and four had inadequate allocation concealment (17 235 women).

There were no differences in perinatal death, hypoxic encephalopathy and neurodevelopmental disability at 12 months of age. The meta-analysis of nine trials showed a decrease of 50% in neonatal seizures (RR 0.50, 95% CI 0.31-0.80). There was a trend towards increased cerebral palsy with continuous CTG (RR 1.74, 95% CI 0.97-3.11). This result is, however, strongly influenced by one small trial, with 35% of the cases excluded after randomization (birth weight >1750 g), analysing data from the remaining cohort of neonates with birth weight between 700-1750 g (6 7). An overall statistically significant increase in caesarean sections (RR 1.66, 95% CI 1.30-2.13) and instrumental vaginal deliveries (RR 1.16, 95% CI 1.01-1.32) in the continuous CTG group, are also presented by the authors of the review.

2. RELEVANCE TO UNDER-RESOURCED SETTINGS

2.1. Magnitude of the problem

Oxygenation of the fetus requires an adequate supply of maternal blood to the placenta, a properly functioning placenta, and a patent umbilical vein in the umbilical cord. Uterine contractions during labour may decrease or stop altogether maternal blood flow to the fetus, compromising fetal well being. Most fetuses have sufficient oxygen reserve to deal with the reduced oxygen supply, but in a limited number of cases fetuses suffer distress from lack of oxygen. Compression of the umbilical cord during labour may also be a cause of fetal distress (8). Several antenatal and intrapartum risk factors have been associated with the development of neonatal encephalopathy, cerebral palsy or even perinatal death (9). However, monitoring of fetal well being has not improved much over the last decades and interventions currently in use in developing countries do not differ significantly from those used many years ago. Moreover, while continuous CTG is widely used in developed countries, its use in many under-resourced settings is infrequent.

2.2. Applicability of the results

Only one of the included trials was conducted in a developing country. This trial included 200 high-risk women (all of whom had meconium stained liquor). Only unpublished data from this trial were available for the authors of the review and the authors considered the trial to have an inadequate concealment of allocation (10).

The other eleven trials were conducted in developed countries, and most of them under strictly controlled research protocols. Thus, the results of this review would not be easily applicable to under-resourced settings, where only a few or no cardiotocographs are available, personnel is limited in number and training, and resources for maintenance and consumables are scarce, in which it would be difficult to replicate the ideal conditions for continuous CTG.

2.3. Implementation of the intervention

The use of continuous CTG in under-resourced settings is not recommended on the basis of the data reviewed here. Policy-makers and health administrators who consider implementing such a policy should take into account the fact that continuous CTG has not been shown to have an overall advantage over the other methods assessed and its introduction would considerably increase the costs of maternal health care. If introduced, a careful evaluation or audit after its implementation should be performed.

3. RESEARCH

Although neonatal seizures were significantly decreased by the use of continuous CTG compared with intermittent auscultation, the factors behind this reduction are not known. To investigate such factors and their potencial long-term consequences, trials with long-term infant follow up are needed.

Moreover, the use of continuous CTG in many hospitals in developing countries, is not a standard procedure and sometimes is never performed. Instead, a combination of intermittent CTG, with intermittent auscultation using handheld devices or Pinard stethoscope between recording periods is in many cases seen and accepted as standard practice. This combination allows to maximise the use of the often scarce number of cardiotocographs and consumables.

Comparisons of continuous versus intermittent CTG did not have sufficient power to detect differences between groups. Future adequately powered RCTs should explore the possibility of comparing the two abovementioned variations of the method in moderate to high risk patients. This comparison should include total health costs evaluation taking into consideration machines, consumables and maintenance of the equipment, as well as the need of proper training on the interpretation of results.

RCTs evaluating the performance of continuous CTG compared to IA in low to high-risk pregnancies with regard to long-term outcomes, cerebral palsy and neurodevelopmental disability should be encouraged. Maternal and health providers' views and satisfaction should also be considered.

References

  • Alfirevic Z, Devane D, Gyte GML. Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour (Cochrane Review). The Cochrane Database of Systematic Reviews Issue 3, 2006;Chichester, UK: John Wiley & Sons.
  • Thacker SB, Stroup D, Chang M. Continuous electronic heart rate monitoring for fetal assessment during labor. The Cochrane Database of Systematic Reviews Issue 2, 2001;Chichester, UK: John Wiley & Sons.
  • Leveno KJ, Cunningham FG, Nelson S, Roark ML, Williams ML, Guzick DS, et al. A prospective comparison of selective and universal electronic fetal monitoring in 34,995 pregnancies. New England Journal of Medicine 1986;315:615-619.
  • Haverkamp AD, Orleans M, Langendoerfer S, McFee J, Murphy J, Thompson HE. A controlled trial of the differential effects of intrapartum fetal monitoring. American Journal of Obstetrics and Gynecology 1979;134:399-412.
  • Herbst A, Ingemarsson I. Intermittent versus continuous electronic fetal monitoring in labour: a randomized study. British Journal of Obstetrics and Gynaecology 1994;101:663-668.
  • Luthy DA, Shy KK, van Belle G, Larson EB, Hughes JP, Benedetti TJ, et al. A randomized trial of electronic fetal monitoring in preterm labor. Obstetrics and Gynecology 1987;69:687-695.
  • Shy KK, Luthy DA, Bennett FC, Whitfield M, Larson EB, van Belle G, et aI. Effects of electronic fetal heart rate monitoring, as compared with periodic auscultation, on the neurologic development of premature infants. New England Journal of Medicine 1990;322:588-593.
  • Neilson JP. Fetal electrocardiogram (ECG) for fetal monitoring during labour. The Cochrane Database of Systematic Reviews Issue 2, 2003;Chichester, UK: John Wiley & Sons.
  • Royal College of Obstetricians and Gynaecologists (RCOG). Use Of Electronic Fetal Monitoring: The use and interpretation of cardiotocography in intrapartum fetal surveillance. Evidence-based Clinical Guideline Number 8. London: Royal College of Obstetricians and Gynaecologists Press;UK, 2001.
  • Azhar NA, Neilson JP. Randomised trial of electronic intrapartum fetal heart rate monitoring with fetal blood sampling versus intermittent auscultation in a developing country. British Journal of Obstetrics and Gynaecology 2001;(unpublished data extracted from Cochrane systematic review):Chichester, UK: John Wiley & Sons.

This document should be cited as: Nardin JM. Continuous cardiotocography (CTG) as a form of electronic monitoring (EFM) for fetal assessment during labour: RHL commentary (last revised: 9 January 2007). The WHO Reproductive Health Library; Geneva: World Health Organization.

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