There is no doubt that standard “wired” CTG monitoring restricts mobility during labour and favours recumbent positions on the bed during labour (Watson, et al., 2022). I often hear people say that this leads to longer labours, contributing to the rise in caesarean section rate seen with CTG monitoring. This post explores the evidence for this from randomised controlled trials comparing intermittent auscultation with continuous CTG monitoring in labour.
Four randomised controlled trials reported on duration of labour. The findings were:
- Renou, et al., 1976 – no significant difference in total labour duration (9.2 hours with CTG monitoring, 9.0 hours with intermittent auscultation)
- Kelso, et al., 1978 – shorter first and second stages of labour with CTG monitoring (first stage 5.9 hours with CTG monitoring, 6.6 hours with intermittent auscultation; second stage 28 mins with CTG monitoring, 32 mins with intermittent auscultation)
- Vintzileos, et al., 1993 – longer first and second stages of labour with CTG monitoring (first stage 6.1 hours with CTG monitoring, 5.5 hours with intermittent auscultation; second stage 29 minutes with CTG monitoring, 27 minutes with intermittent auscultation)
- Herbst, et al., 1994 – no significant difference in labour durations or incidence of prolonged labour (first stage 3.5 hours with CTG monitoring, 4 hours with intermittent auscultation; second stage 0.4 hours with CTG monitoring, 0.48 hours with intermittent auscultation; labour longer than 12 hours 16% of women with CTG monitoring, 16% with intermittent auscultation)
Taken together, these findings show no differences in labour durations between the two approaches to fetal heart rate monitoring in labour.
Use of oxytocin in labour
But hang on, I hear you say – when labour starts to slow, we typically use oxytocin to speed it back up again. Could the absence of difference in labour duration be because oxytocin was used more often when CTG monitoring was in use? The Alfirevic, et al., 2017 Cochrane review has an analysis relating to oxytocin use (analysis 1.19). Five randomised controlled trials contributed data. There was no significant difference in the use of oxytocin during labour between the CTG monitoring (50%) and intermittent auscultation groups (43%). So that’s not why there is no difference in labour duration.
Caesarean section for labour dystocia
But hang on, I hear you say once again. What if labour was shortened by more frequent caesarean section for labour dystocia in the CTG monitoring group and that was impacting on labour duration? Five of the randomised controlled trials reported on the use of caesarean section specifically for delays in labour. The findings were:
- Renou, et al., 1976 – no significant difference (15% with CTG monitoring, 11% with intermittent auscultation)
- Macdonald, et al., 1985 – no significant difference (1.3% in both the CTG monitoring and intermittent auscultation groups)
- Neldam, et al., 1986 – no significant difference (9% with CTG monitoring, 8% with intermittent auscultation)
- Leveno, et al., 1986 – no significant difference (4.8% with universal CTG use, 4.9% with selective CTG use)
- Luthy, et al., 1987 – no significant difference (3.3% with CTG monitoring, 2.4% with intermittent auscultation)
Once again, there is no evidence here that CTG monitoring is prolonging labour leading to caesarean section for labour dystocia.
But hang on…
There is therefore no evidence from randomised controlled trials to show CTG monitoring is associated with prolonged labour when compared with intermittent auscultation. Why does it seem from clinical practice it does then? It is possible the context of practice has changed, and that might impact on the relationship between labour duration and the type of fetal heart rate monitoring used.
Internal fetal heart rate monitoring with a fetal spiral electrode was the most common approach to CTG monitoring, and a Pinard was the most commonly used means to perform intermittent auscultation in the trials. It is difficult to perform intermittent auscultation with a Pinard when the woman is in any position other than semirecumbent. Most of the randomised controlled trials were conducted at times and in environments where it was common for all women to remain recumbent on the bed during labour – irrespective of the approach to fetal heart rate monitoring. As a consequence, women in the intermittent auscultation groups in the randomised controlled trials may have had fairly limited mobility reducing the potential for a difference in labour duration secondary to this.
If you are a researcher investigating women’s experiences of intrapartum fetal heart rate monitoring with newer technologies (like telemetry or noninvasive fetal ECG monitoring) I would encourage you to gather data about labour duration, augmentation, and labour dystocia. It would be very useful to know whether these new approaches make a difference to these outcomes, or not.
Watson and colleagues study of telemetry CTG monitoring did this (2022). They reported the length of first stage was 5 hours when telemetry was used and 4.4 hours with wired CTG monitoring. Second stage duration was 1.4 hours with telemetry and 0.9 hours with wired CTG monitoring. Amniotomy and oxytocin use was similar in both groups. The caesarean section rate was higher when telemetry monitoring was used (22% rather than 14% for wired CTG monitoring). Given they also found that women using telemetry were far more likely to labour off the bed, these findings run counter to what would be expected.
Watson’s study was not an randomised controlled trial, so there may be important differences between women who chose telemetry and those who did not to explain the findings. But it certainly dose pose interesting questions. It would be good to have robust evidence about the relationship between mobility and labour positions and labour duration, and the impact that different forms of fetal heart rate monitoring have on this relationship.
Alfirevic, Z., Devane, D., Gyte, G. M. L., & Cuthbert, A. (2017). Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour. Cochrane Database of Systematic Reviews, 2(CD006066), 1-137. https://doi.org/10.1002/14651858.CD006066.pub3
Herbst, A., & Ingemarsson, I. (1994). Intermittent versus continuous electronic monitoring in labour: a randomised study. British Journal of Obstetrics & Gynaecology, 101(8), 663-668. https://doi.org/10.1111/j.1471-0528.1994.tb13181.x
Kelso, I. M., Parsons, R. J., Lawrence, G. F., Arora, S. S., Edmonds, D. K., & Cooke, I. D. (1978). An assessment of continuous fetal heart rate monitoring in labor. A randomized trial. American Journal of Obstetrics & Gynecology, 131(5), 526-532. https://doi.org/10.1016/0002-9378(78)90114-x
Leveno, K. J., Cunningham, F. G., Nelson, S. M., Roark, M., Williams, M. L., Guzick, D., Dowling, S., Rosenfeld, C. R., & Buckley, A. (1986). A prospective comparison of selective and universal electronic fetal monitoring in 34,995 pregnancies. New England Journal of Medicine, 315(10), 615-619. https://doi.org/10.1056/NEJM198609043151004
Luthy, D. A., Shy, K. K., van Belle, G., Larson, E. B., Hughes, J. P., Benedetti, T., Brown, Z. A., Effer, S., King, J. F., & Stenchever, M. A. (1987). A randomized trial of electronic fetal monitoring in preterm labor. Obstetrics & Gynecology, 69(5), 687-695. https://www.ncbi.nlm.nih.gov/pubmed/3554055
MacDonald, D., Grant, A., Sheridan-Pereira, M., Boylan, P. C., & Chalmers, I. (1985). The Dublin randomized controlled trial of intrapartum fetal heart rate monitoring. American Journal of Obstetrics & Gynecology, 152(5), 524-539. https://doi.org/0002-9378
Neldam, S., Osler, M., Hansen, P. K., Nim, J., Smith, S. F., & Hertel, J. (1986). Intrapartum fetal heart rate monitoring in a combined low- and high-risk population: a controlled clinical trial. European Journal of Obstetrics, Gynecology, & Reproductive Biology, 23(1-2), 1-11. https://doi.org/10.1016/0028-2243(86)90099-7
Renou, P., Chang, A., Anderson, I., & Wood, C. (1976). Controlled trial of fetal intensive care. American Journal of Obstetrics & Gynecology, 126(4), 470-476. https://doi.org/10.1016/0002-9378(76)90641-4
Vintzileos, A. M., Antsaklis, A., Varvarigos, I., Papas, C., Sofatzis, I., & Montgomery, J. T. (1993). A randomized trial of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation. Obstetrics & Gynecology, 81(6), 899-907. https://www.ncbi.nlm.nih.gov/pubmed/8497353
Watson, K., Mills, T. A., & Lavender, T. (2022). Experiences and outcomes on the use of telemetry to monitor the fetal heart during labour: findings from a mixed methods study. Women & Birth, 35(3), e243-e252. https://doi.org/10.1016/j.wombi.2021.06.004