Birth Small Talk

Talking about birth

What about CTG monitoring for VBAC?

White goat looking directly to camera with an expression like it is wondering what nonsense the humans are getting up to this week.
Photo by Sergiu Vălenaș on Unsplash

One of the questions I am often asked about is what research says is the best approach to fetal heart rate monitoring for a woman who has previously had one (or possibly more) caesarean births in the past and plans a vaginal birth this time around. There is no simple answer to this question, so it is one I have avoided writing about. Up until now. A new piece of research has prompted me to address this topic. Today’s post explores what we do and do not know from research to answer the question about whether a woman planning vaginal birth after caesarean section will benefit from CTG use.

Why are women planning vaginal birth after caesarean section advised to have CTG monitoring in labour?

All major international fetal monitoring guidelines advise that women planning vaginal birth after caesarean section have intrapartum CTG monitoring for the duration of their labour. Women planning vaginal birth after one previous caesarean section are slightly more likely to experience stillbirth, neonatal death, or to have a baby with hypoxic ischaemic encephalopathy than women who plan to have a caesarean section prior to labour. Most of the difference relates to the chance of stillbirth before labour starts, which inevitably occurs at a later gestational age for women who wait for labour to start. The large study on outcomes by Landon, et al., in 2004 found an antenatal stillbirth rate of 22 per 10,000 for women planning vaginal birth and 9 per 10,000 for women planning caesarean section.

In Landon’s study, intrapartum stillbirth occurred at a rate of 1 per 10,000 for women planning vaginal birth, with none occurring for women planning caesarean birth. The neonatal death rate was 8 per 10,000 for planned vaginal birth and 5 per 10,000 for caesarean section. A more recent Scottish study (Fitzpatrick, et al., 2019) reported a combined intrapartum stillbirth plus neonatal death rate of 7 per 10,000 for planned vaginal birth and 1 per 10,000 for planned caesarean birth. Not all studies have found a higher intrapartum stillbirth rate. The one I wrote about last week showed no higher risk for intrapartum stillbirth after a previous caesarean section (occurring at a rate of 8 per 10,000), but a really high risk (19 times more likely) if uterine rupture happened (Davidesko, et al., 2022).

Uterine rupture rates in Landon’s study were 69 per 10,000 in the planned vaginal birth group and zero in the planned caesarean group. In Fitzpatrick’s study, they were 24 per 10,000 and 4 per 10,000 respectively. Hypoxic ischaemic encephalopathy rates in Landon’s study were 8 per 10,000 for planned vaginal birth with no cases for planned caesarean section. Just over half these cases happened after uterine rupture occurred. None of the intrapartum stillbirths in Landon’s study were related to uterine rupture (that’s not to say they don’t happen, just that it is rare enough not to turn up in this study), and 15% of neonatal deaths were preceded by uterine rupture.

So in summary, yes, women planning vaginal birth after caesarean section are (compared to women planning caesarean section) more likely to experience outcomes that CTG monitoring has been proposed to help prevent. However, the highest risk of death occurs before labour and is therefore not modifiable by CTG monitoring in labour.

What does the evidence from randomised controlled trials say?

There’s only ever been one randomised controlled trial were all the women in the trial had previously given birth by caesarean section and were planning vaginal birth. This was published by Madaan and Trivedi in 2006. The trial was too small to show very much on its own – with only 50 women randomly allocated to CTG monitoring and 50 to IA. No one experienced uterine rupture, and there were no deaths. There were no differences in the rate of low Apgar scores, “birth asphyxia”, or admission to the nursery. While the rate of caesarean section was higher for women allocated to CTG monitoring (34% rather than 22%) this did not reach statistical significance.

When we look at the larger body of research about CTG monitoring focussing on women considered to be at higher risk, can we learn anything from it that might be useful to apply for women planning vaginal birth after caesarean section? The caesarean section rates in these trials were far lower than is current practice, for example the large Dublin trial (MacDonald et al., 1985) had an overall caesarean section rate of 2% in their mixed risk population. None of the inclusion or exclusion criteria describing who was or was not in the trials makes any mention of previous caesarean section (with the exception of the Madaan and Trivedi trial) so it is impossible to know whether any women with a previous caesarean section made up any of the trial populations. If they did, there were likely to be very small in number.

We know that overall the trials found that CTG monitoring did not reduce the rate of stillbirth, neonatal death, or hypoxic ischaemic encephalopathy, but did lower the rate of neonatal seizures by 15 per 10,000 births. We can’t know whether this applies, or not, to women planning vaginal birth after caesarean section because we don’t have enough data. That leads to two possible philosophical approaches to how to approach practice in the absence of any evidence. Option 1 is to default to IA given that there is no evidence to support that CTG monitoring produces a benefit. Option 2 is to default to CTG monitoring given that there is no evidence to support that IA is any safer than CTG monitoring. Let’s be clear then, that our professional guidelines are demonstrating their philosophical belief in the superiority of CTG technology, not generating an evidence-based argument, because there is not one to be generated. That’s OK – guidelines can still provide guidance in the absence of evidence. But it would be nice if they were up front about it, rather than claiming to be evidence based.

Can CTG monitoring predict uterine rupture before it happens?

Given that uterine rupture occurs more often during planned vaginal birth than it does when women plan to have a prelabour caesarean section, and it strongly linked to poor outcomes for the baby, it has been argued that CTG monitoring might predict uterine rupture is about to happen before it can be detected based on other signs (like pain and bleeding)and therefore reduce the chance of a poor outcome for the baby. If this is true, then at least theoretically, CTG monitoring might help to prevent death or brain injury for the fetus if maternity professionals can act faster. This is where the new research that prompted me to write this post fits in.

A team of Danish researchers attempted to answer the question of whether CTG monitoring could predict uterine rupture for women planning vaginal birth after caesarean section (Andersen, et al., 2022). They started by identifying women who gave birth between 1997 and 2008, had previously had a caesarean section, had CTG monitoring during labour, and experienced uterine rupture. They found 53 cases. They then selected 43 controls, being women who were the next after each of the cases to have a vaginal birth after caesarean section without uterine rupture, and who had a complete CTG recording.

Identifying details were removed from the CTG recordings, and the last 4 hours of the trace were sent to 19 obstetricians who did not know any clinical details about the woman or her birth. The obstetricians were asked to use the FIGO guideline to classify each 30 minute segment of the CTG as normal, suspicious, pathological, or pre-terminal and to describe the individual features of the CTG (like the baseline and the type of any decelerations). It is important to know that outcomes for the babies were worse in the cases than the controls, with 10% (versus 2%) of the cases ending in stillbirth or neonatal death, 38% (versus 5%) having a low Apgar score, and 34% (vs 2%) having cord blood acidosis. These were not “harmless” cases of uterine rupture discovered as an incidental finding.

The rate of CTG abnormalities was high – with only two controls and none of cases having a CTG trace that remained normal at all times in the four hours before birth. Suspicious traces were seen equally in both cases and controls (53 and 49%). Pathological traces were present in 77% of the cases and 53% of the controls. While there were some changes in particular CTG features that happened more often for cases than for controls (tachycardia, reduced variability, and severe variable decelerations), these features were also common in CTG traces from controls (tachycardia in 23%, reduced variability in 35%, severe variable decelerations in 51%). Tachysystole (too many contractions close together) was as common in cases (55%) as it was in controls (50%).

The authors wrote in their conclusion:

A pathological cardiotocogram should lead to particular attention on threatening uterine rupture but cannot be considered a strong predictor as it is common in all women with a trial of labour after caesarean delivery.

p. 2

You know what really gets my goat?

So here we are – with almost no research about the best approach to fetal heart rate monitoring for women in labour who have previously given birth by caesarean section, and evidence that CTG monitoring doesn’t reliably predict uterine rupture. And really, really no evidence at all for women who had had more than one previous caesarean section. In the face of such uncertainty, I would hope to see professional guidelines recognising that the decision about fetal monitoring approach rests entirely on the philosophical beliefs of the decision-maker, and the person best placed to make that decision would be the woman giving birth. Sadly, that’s far from the case.

I once worked in a private hospital where I was told by senior management that any woman with risk factors (like a previous caesarean section) would be refused admission if she did not agree in advance to have CTG monitoring. I have had stories shared with me about women who were told that they would be refused the option of vaginal birth if they did not agree to have CTG monitoring or where CTG monitoring was used as a bargaining chip to argue over access to another approach that women wanted to use during labour. These experiences pop up in research too, like this quote from a woman in Townsend and colleagues new research about women seeking water immersion for their vaginal birth after caesarean section (the airy-fairy stuff being water immersion):

He [the Obstetrician] said that I could have all my fluffy fuddy-duddy things if I wanted them, but he didn’t care about that. As long as I was having the VEs [vaginal examinations] and I was having the [intravenous] cannula, and I was having constant [baby’s heart rate] monitoring, then he would let me in the water. As long as I played by his rules, he was okay if I wanted the airy-fairy stuff.

Townsend, et al., 2022, p. 7

And that’s what really gets my goat. The question of CTG monitoring for vaginal birth after caesarean section is as close to an evidence-free zone as we get in maternity care. Maternity professionals should know that there is no good evidence to inform practice in this situation. Maternity professionals should be communicating that as part of their information-sharing conversations with women as they make decisions about their upcoming birth. Maternity professionals should be supportive of whatever decisions women make about fetal heart rate monitoring for their vaginal birth after caesarean section, given that no one approach has proven benefit over the other. And maternity professionals should not be withholding access to water immersion (or any other form of care) as punishment for women who do not comply with CTG monitoring. If you are a birthing woman, and this is happening or has happened to you, know that this is not OK.


Andersen, M. M., Thisted, D. L., Amer-Wahlin, I., Krebs, L., & Danish CTG Monitoring during VBAC study group. (2016). Can intrapartum cardiotocography predict uterine rupture among women with prior caesarean delivery?: A population based case-control study. PLoS ONE, 11(2), e0146347. 

Davidesko, S., Levitas, E., Sheiner, E., Wainstock, T., & Pariente, G. (2022). Critical analysis of risk factors for intrapartum fetal death. Archives of Gynecology & Obstetrics, in press.

Fitzpatrick, K. E., Kurinczuk, J. J., Bhattacharya, S., & Quigley, M. A. (2019). Planned mode of delivery after previous cesarean section and short-term maternal and perinatal outcomes: A population-based record linkage cohort study in Scotland. PLoS Med, 16(9), e1002913.

Landon, M. B., Hauth, J., Leveno, K. J., Spong, C. Y., Leindecker, S., Varner, M. W., Moawad, A., Caritis, S. N., Harper, M., Wapner, R. J., Sorokin, Y., Miodovnik, M., Carpenter, J. D., Peaceman, A. M., O’Sullivan, M. J., Sibai, B. M., Langer, O., Thorp, J. M., Ramin, S. M., Mercer, B. M., Gabbe, S. G., & National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. (2004). Maternal and perinatal outcomes associated with a trial of labor after cesarean delivery. New England Journal of Medicine, 351(25), 2581-2589. 

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.

Madaan, M., & Trivedi, S. S. (2006). Intrapartum electronic fetal monitoring vs. intermittent auscultation in postcesarean pregnancies. International Journal of Gynecology & Obstetrics, 94(2), 123-125. 

Townsend, B., Fenwick, J., McInnes, R., & Sidebotham, M. (2022, Aug 1). Taking the reins: A grounded theory study of women’s experiences of negotiating water immersion for labour and birth after a previous caesarean section. Women & Birth, in press. 

Categories: CTG, EFM, IA, New research, Perinatal brain injury, Perinatal mortality, Stillbirth

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2 replies

  1. Thank you for this post. I’m currently planning my VBAC, and as a doctor myself (and married to one!), I was finding it hard to convince myself of IA vs CTG and birthing outside guidelines. I have been told I need continuous monitoring, without any of this background, so definitely not informed choice. This has armed me with the knowledge I needed to make my decision for my birth.


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