Is “loss of contact” a good thing or a bad thing?

I scanned the abstract of this paper when I first saw it (Roth et al., 2026), and thought it is was interesting enough to add to my list of papers that might make it as a blog post. Today as I read the detail of the paper, I found myself thinking “ooo, that’s fascinating!” and “I had not realised how little evidence we have about that”. (Which frankly should no longer surprise me, yet here we are…)

So what’s this paper about? Signal loss when external CTG monitoring is used in labour. In other words, they wanted to find out just how often there were gaps in the heart rate tracing (called loss of signal in this paper, also often called loss of contact), what factors made these more likely, and whether they were linked to worse outcomes for women and babies.

There’s a strong belief that it is important to capture EVERY single fetal heart beat from pretty much the moment the woman walks into a maternity service in labour until the time the baby is born, and that failing to do so means that poor outcomes are more likely. I have seen first hand the way that central fetal monitoring systems interact with this belief – when professionals look at the trace from outside the room, gaps in the trace are more noticeable. The absence of the rest of the contextual information found inside the room tends to drive the use of fetal spiral electrodes and other interventions.

The authors started with a review of previous research. This is what alerted me yet another gaping hole in the CTG monitoring mythology. They cited only two studies that had investigated this topic in the past, one from 2004 in English, the other from 2008 in French. I had a quick look at both papers. The second was actually a literature review rather than research, and it included the 2004 paper plus a few other even older studies. The 2004 paper examined CTG traces from 239 women, looking at how often there were quality issues with trace, but didn’t look to see if this had any impact on outcomes. Once again we see something that is taken as a proven truth ending up with no solid ground underneath it.

Let’s look to see if this new research from Austria provides us with some substance for the concern about gaps in the CTG recording.

How was the research done?

CTG recordings from 303 women were retrospectively analysed. All women had used external monitoring only, were 18 years of age or more, at least 36 weeks pregnant, and in either spontaneous or induced labour. All women had given prior consent for the use of their data for research (yay! – nice to see high ethical research standards).

An independent investigator who was blinded to outcomes examined the recordings. Paper speeds were set at 1 cm per minute, so each 1mm space represented six seconds. Any gap in the heart rate trace of 1 mm or more was counted. They split the recordings into two groups, those with more than 20% of the total recording time missing and those with less than 20% missing.

What they found

Only four of the 303 recording had no gaps (1.3%), with the proportion of the trace that was missing ranging from less than 1% to 52%. The average duration of the recordings was 5.5 hours. 18% of the CTGs had more than 20% of the trace missing.

Gaps in the recording were more common during the placement of an epidural and during active pushing. There were no associations with body mass index, induction of labour, or gestational age, but they were more likely in multiparous women and those who were not using an epidural. Shorter labours (both overall and the pushing stage) were seen in women with more missing segments in the CTG. There was also a higher rate of spontaneous vaginal birth.

There were no statistically significant differences in outcomes for babies between the women with more, or less, than 20% of the fetal heart rate recording missing. This is mostly a mathematical effect as the numbers of babies with poor outcomes was small.

The raw numbers are interesting though – as they are not what you would expect. Cord pH was 7.27 in the group with more gaps in the CTG and 7.25 in those with less gaps. Lactate levels were lower in the group with more gaps (3.2 rather than 3.5). Overall, nine babies were admitted to the neonatal unit but only one was in the group with more than 20% of gaps in the trace. The only baby to have an Apgar of under 7 at 5 minutes of age was in the group with fewer gaps. When these were all merged into a composite outcome, 37 babies in the group with fewer gaps had a poor outcome and only four in the group with more gaps.

What does this mean for CTG monitoring?

The authors, correctly, were cautious to point out that this should not be taken to mean that having gaps in the CTG trace is a great idea. Multiparous women were more likely to have gaps in the trace – and they also have shorter labours, a lower caesarean birth rate, and better outcomes for their babies.

The authors also pointed out that central fetal monitoring and staffing levels may explain the higher proportion of gaps in the CTG in women who did not have epidurals. One-to-one care was described as “very rare”, and many women would spend significant periods of time unattended. Having an epidural triggered more constant attention and therefore adjustment of the Doppler resulting in a better quality trace. These findings therefore need to be applied with caution in maternity services where one-on-one labour care is the norm. We should be staffing maternity services to this level as there are a myriad of safety and satisfaction reasons for doing so.

No one should look at this study and decide that leaving the Doppler sensor on the CTG dangling in thin air for long periods of time is a stunningly good way to achieve good perinatal and maternal outcomes. BUT – this study certainly does nothing to validate the belief that recording the fetal heart rate for more of the time leads to better outcomes than recording it less of the time.

What this means for intermittent auscultation?

One of the arguments made for the superiority of CTG monitoring is the “continuous” nature of the heart rate recording. This study verifies that the description “continuous fetal monitoring” is more aspirational than a reflection of the reality for most women with external monitoring.

The gaps in the CTG recording measured for this study were unintentional, with the possibility that data might not be recorded at critical moments during the labour. With intermittent auscultation, someone makes a deliberate decision about when to start and when to stop listening to the fetal heart rate. With appropriate staffing and knowledgable staff performing intermittent auscultation there is no logical reason to believe that perinatal outcomes will be worse than with CTG use.

Confident Intermittent Auscultation: Live is coming back! This is my two-hour long, online workshop that will build your knowledge and confidence with intermittent auscultation so you can offer it to more women in your practice. Enrolments just opened. (This workshop came close to selling out last time I ran it, and it may well sell out this time. Don’t wait until the last minute to register as I have capped the number of places!)

The workshop will be on: Thursday May 21, at 7 pm (AEST, Brisbane time, GTM+10)

One of the things I include in the workshop is a physiology-based approach to WHEN you should be listening to the fetal heart rate and for HOW LONG – so you can gather the same quality (rather than quantity) of information that others get from a CTG recording. If that interests you – register at the link below for more details. (Yes, there will be a recording available.)

Confidence is just around the corner…

Learn more

References

Roth, G. E., Laurent, A., Goetsch, T., Silva, I. D., & Voillequin, S. (2026). Signal loss during external cardiotocography in labor: a retrospective quantitative study. Journal of Gynecology, Obstetrics & Human Reproduction, 103197. https://doi.org/10.1016/j.jogoh.2026.103197