Don’t miss a beat! Does continuous heart rate monitoring matter?

There’s pressure on maternity professionals to make sure that pretty much every fetal heart beat gets recorded during labour. The term “loss of contact” is used to refer to a break in the fetal heart rate recording and these are seen as a Bad Thing ™. In my experience, short gaps in the heart rate recording have become even less tolerated with the introduction of central fetal monitoring. Without the contextual information available in the birth room, the viewer at the central monitoring station wants to see more of the heart rate to be able to determine what to make of the CTG trace.

What happens then?

The desire to not miss a single heart beat drives several changes in clinical care. The first is likely to be the midwife touching the woman and repositioning the Doppler heart rate sensors. If this doesn’t resolve the problem, the midwife will hold the sensor in place, achieving an angle that isn’t possible with the straps usually used to hold the sensor. They might delegate this task to the woman or to another person. These small actions start to send the message to the woman that capturing every heart beat now has priority over the woman’s comfort, her choice of position, and her freedom of movement.

If that isn’t successful at improving the completeness of the CTG, then the next step is to suggest (or sometimes insist on) the placement of a fetal spiral electrode. While these are better at achieving a continuous CTG (Euliano et al., 2017), they are a more substantial intervention that takes birth further away from being physiological. Using a fetal spiral electrode introduces the potential for complications like scalp trauma, and infection for either (or both) the woman and the baby (Fick & Woerdeman, 2021; Harper et al., 2013; Kawakita et al., 2016).

And sometimes, I have seen women pressured into caesarean section simply because it was difficult to record the heart rate continuously with any method.

Where’s the proof?

Let’s look for evidence that having a more complete heart rate recording is associated with better outcomes for the fetus / baby without substantially increasing the chance of harm for the woman being monitored. That’s a bit tricky. There’s never been a study that started with a group of women with frequent episodes of “loss of contact” on their CTG, and randomised them to use of a fetal spiral electrode or to continue with external CTG monitoring, and looked to see what impact this had on outcomes. Nor has there ever been a randomised controlled trial looking to see whether there are different outcomes for the baby when using a fetal spiral electrode compared with an external Doppler heart rate sensor.

But we do have some research that can point us in the right direction, in the absence of these more definitive forms of proof. First, there has been one trial comparing intermittent CTG with continuous CTG use (Herbst & Ingemarsson, 1994), also described in the Cochrane review about CTG monitoring (Alfirevic et al., 2017). Women in this trial were at “low to moderate risk” and were randomly assigned to either “continuous” CTG monitoring, or to a CTG trace of 10 to 30 minutes duration every two to two and a half hours, with the heart rate being auscultated every 15 to 30 minutes when the CTG was not in use. They checked to see that there really was a difference in how much time the CTG was in use between the two groups and there was – 68% of the duration of labour in the “continuous” group, and 47% of labour in the intermittent group.

They found no significant differences in cord blood gas results, Apgar scores, or admissions to the neonatal nursery, with the trend being towards better outcomes with intermittent rather than continuous CTG use. The caesarean section rate in the “continuous” monitoring group was 2.4% and in the intermittent group it was 1.8% (the difference doesn’t reach statistical significance). Importantly, no evidence suggesting that care was delayed in the intermittent auscultation group was found, with the authors saying:

In no case was an emergency caesarean section for fetal distress performed for fetal heart rate abnormalities when [CTG] monitoring was started after a period of normal fetal heart rate auscultation.

Next, there is research that has compared continuous CTG use with intermittent auscultation, and that shows no fetal benefit. This research also showed higher rates of caesarean section and instrumental birth with CTG use. I won’t run through the details here – as I have presented that evidence multiple times on the blog already. You can double check these findings in the Cochrane review (Alfirevic et al., 2017).

Finally, there’s evidence from a study from Ireland that looked at how often certain fetal heart rate patterns were seen in labour, both for babies with a diagnosis of neonatal encephalopathy (a sign of brain injury) and for healthy babies (Reynolds et al., 2022). For babies with neonatal encephalopathy, 10% of the CTG trace during labour was categorised as uninterpretable. There are several reasons why this might have been the case and “loss of contact” is likely to have been a major contributor. For healthy babies, the proportion of the CTG that was uninterpretable was also 10%. So there’s nothing from this study to suggest that missing bits of information on the CTG from time time leads to babies having worse outcomes.

What does all this mean?

There is no evidence that supports the argument that capturing more of the heart rate during labour leads to better outcomes for the baby than if you are only capturing that information some of the time for the vast majority of women. There is evidence that using fetal spiral electrodes can lead to complications for some women and some babies.

Aggressively pursuing an uninterrupted fetal heart rate trace is a symptom of a maternity care system that is asking the wrong question. Instead of asking – is this fetus okay? – the question has shifted to – is this CTG okay? That’s a very different thing. Short periods of focussed listening to the fetal heart rate at key times, along with looking for other evidence of fetal wellbeing or for problems, is the evidence-based approach to fetal monitoring in labour. Simply generating a pretty looking wiggly line all the time does nothing to guarantee safe maternity care.

Are you planning your birth and looking for evidence-based information about the different fetal heart rate monitoring options for labour? I have a course specifically for you, designed to support YOU to be the person who makes decisions about which type of fetal heart rate monitoring to use.

Tell me more!

References

Alfirevic, Z., Devane, D., Gyte, G. M. L., & Cuthbert, A. (2017, Feb 03). 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

Euliano, T. Y., Darmanjian, S., Nguyen, M. T., Busowski, J. D., Euliano, N., & Gregg, A. R. (2017). Monitoring fetal heart rate during labor: A comparison of three methods. Journal of Pregnancy, 2017(6), 8529816-8529815. https://doi.org/10.1155/2017/8529816

Fick, T., & Woerdeman, P. A. (2021, Apr 6). Neonatal brain abscess development following fetal scalp electrode placement: a rare complication. Child’s Nervous System, 38(1), 199-202. https://doi.org/10.1007/s00381-021-05150-7

Harper, L. M., Shanks, A. L., Tuuli, M. G., Roehl, K. A., & Cahill, A. G. (2013, Jul). The risks and benefits of internal monitors in laboring patients. American Journal of Obstetrics & Gynecology, 209(1), 38.e31-36. https://doi.org/10.1016/j.ajog.2013.04.001

Herbst, A., & Ingemarsson, I. (1994, Aug 01). 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

Kawakita, T., Reddy, U. M., Landy, H. J., Iqbal, S. N., Huang, C.-C., & Grantz, K. L. (2016, Oct). Neonatal complications associated with use of fetal scalp electrode: a retrospective study. BJOG: An International Journal of Obstetrics and Gynaecology, 123(11), 1797-1803. https://doi.org/10.1111/1471-0528.13817

Reynolds, A. J., Murray, M. L., Geary, M. P., Ater, S. B., & Hayes, B. C. (2022, Jun). Fetal heart rate patterns in labor and the risk of neonatal encephalopathy: A case control study. European Journal of Obstetrics & Gynecology and Reproductive Biology, 273, 69-74. https://doi.org/10.1016/j.ejogrb.2022.04.021