Does CTG monitoring during labour save lives?

Today’s post is a revision of a post from 2200. It examines the research evidence about CTG monitoring with regards to stillbirth and neonatal death. This is a deep dive for my fellow data geeks who like to read the fine print.

What evidence do we currently have that helps us to understand the question of whether CTG monitoring can save lives (or not)? Let’s begin with the randomised controlled trials in the 2017 Alfirevic et al. Cochrane review. Of the eleven randomised controlled trials that compared CTG monitoring with intermittent auscultation (IA) during labour, two were done in low risk populations, five in high risk populations and the remaining four in mixed risk populations or where risk was not specified (Alfirevic et al., 2017). One of the mixed risk trials reported outcomes for a low risk subset separately.

Mortality rates in low risk populations

This is considered the least controversial area of evidence.

A total of 16,049 births provided data for the outcome of perinatal mortality (stillbirth in labour plus neonatal death in the first week of life). There was no statistically significant difference in the perinatal mortality rate (6 per 10,000 in the CTG group, 7 per 10,000 in the intermittent auscultation group, risk ratio 0.87, 95% confidence intervals 0.29 – 2.58).

In summary – CTG monitoring was no better than intermittent auscultation when it comes to preventing death.

Looking specifically at stillbirth in the low risk population

From time to time I see academic writers (who should know better) repeat the myth that CTG monitoring can prevent stillbirth during labour. I think the reason this fallacy persists is that the Cochrane review doesn’t provide separate analyses for stillbirth and neonatal mortality. People can therefore continue to hold the unchallenged belief that while CTG monitoring doesn’t reduce neonatal death, it does prevent stillbirth.

I have gone back to the primary sources (Kelso et al., 1978; Leveno et al., 1986; Wood et al., 1981) and pulled out the numbers for stillbirth and neonatal death separately. I then repeated the meta-analysis, using the same risk breakdown used in the Cochrane review. There were no stillbirths in any of these studies, so the perinatal mortality rate reported in the Cochrane review comes entirely from neonatal deaths. While these results provide no evidence that intermittent auscultation performs as well as CTG monitoring for the prevention of stillbirth – they certainly do not prove that CTG monitoring is better.

Is this still relevant?

It has been almost 40 years since the last of these trials was performed. It could be argued that CTG technology has improved, or that we are better at CTG interpretation now. Heelan-Fancher et al. (2019) examined a large population data set from two states in the United States, specifically looking at birth outcomes for low risk women. This was not a randomised controlled trial – rather it was a non-experimental analysis of what happens in practice when women are monitored by CTG or by intermittent auscultation, with a very large sample size (1.5 million births). They didn’t report on stillbirth during labour. They found no significant difference in the neonatal mortality rate when CTG monitoring was used.

On the basis of available evidence, there is nothing that suggests that use of CTG monitoring rather than intermittent auscultation reduces the perinatal mortality rate in women considered to be at low risk. That’s not all that controversial. Most people in maternity care know this particular bit of information.

Mortality rates in mixed, unknown, and high-risk populations

There is a widespread assumption that CTG monitoring reduces the possibility of death of the fetus or baby in women considered to be a high risk. We wouldn’t be using CTGs so widely if they didn’t save lives, right? Let me take you through what the research says for this group of women.

The randomised controlled trial evidence regarding high risk populations consists of five studies published over 6 papers, over a thirty-year period, starting in 1976 and continuing to 2006 (Haverkamp et al., 1979; Haverkamp et al., 1976; Luthy et al., 1987; Madaan and Trivedi, 2006; Renou et al., 1976; Shy et al., 1987). In addition, there are four studies published over five papers which were conducted in populations made up of a mixture of women at lower and higher risk or where the risk profile of the population was not described (Grant et al., 1989; Kelso et al., 1978; MacDonald et al., 1985; Neldam et al., 1986; Vintzileos et al., 1993). With my co-authors Associate Professor Mary Sidebotham, Professor Jenny Gamble, and Professor Jennifer Fenwick, we synthesised the findings from these populations (Small et al., 2020).

In the high-risk population (n = 1,975), perinatal mortality was not significantly different when CTG was compared with IA (245 per 10,000 in the CTG group, 287 per 10,000 in the intermittent auscultation group, risk ratio 1.17, 95% confidence interval 0.62 – 2.22). There was also no statistically significant difference in mortality in the mixed-risk population (n = 15,994, 23 per 10,000 in the CTG group, 34 per 10,000 in the intermittent auscultation group, risk ratio 0.67, 95% confidence interval 0.36 – 1.23).

What about stillbirths?

In the high risk population, there was no difference in the stillbirth rate between the group with CTG monitoring and those with intermittent auscultation (10 per 10,000 in the CTG group, 13 per 10,000 in the intermittent auscultation group, risk ratio 0.77, 95% confidence interval 0.05 – 12.29). This was also the case for the mixed and unknown risk population (4 per 10,000 in the CTG group, 7 per 10,000 in the intermittent auscultation group, risk ratio 0.59, 95% confidence interval 0.14 – 2.49).

Note that the number of women in these higher risk populations were small. It has been argued that with a larger sample size a difference in stillbirth rates would be detected. To get to the largest possible sample size from the existing evidence, I have added up all the births from across all risk categories, and included all the data from the Leveno et al, 1986 trial (where the comparison was between time periods with more, or less, CTG use). This trial adds an additional 34,995 births to the data set.

Running that analysis gives a total data set of 54,025 births. The stillbirth rate in the CTG group was 12 per 10,000. And in the intermittent auscultation group, it was also 12 per 10,000. The risk ratio was 1.04 with 95% confidence intervals of 0.64 – 1.71. Once again – there was no difference in the stillbirth rate between the two different approaches to fetal heart rate monitoring. There is also no hint of a suggestion that stillbirth rates are better in the CTG monitoring group and it is simply a mathematical issue of insufficient sample size to get to a point where a statistically significant difference is present.

Other research

Even in the face of all of this evidence, I still see arguments that CTG monitoring really does prevent stillbirth because the evidence from research that was done using approaches other than a randomised controlled trial is so compelling. We set out to find and analyse all these other studies to see if that was true or not (Small et al., 2020).

Our searches located 27 papers published between 1972 and 2018 that provided evidence about the use of CTG monitoring during labour in high-risk populations. We then used a tool (ROBINS-I) to assess the degree to which the findings of the research might be affected by bias – that is that the findings were due to something other than CTG use. 22 papers were at critical risk of bias and another was a serious risk. Most of these papers compared a time period prior to the introduction of CTG monitoring with a period after it was introduced, without controlling for any of the other changes to practice which might improve outcomes over time. The remaining five studies were assessed to be at moderate risk of bias. According to the ROBINS-I tool, studies at moderate risk of bias can be relied upon to inform clinical practice.

In the studies at moderate risk of bias (which ranged in size from 235 to 1.2 million women), no significant differences in stillbirth, neonatal mortality, or perinatal mortality rates were reported.

So no matter which way I have attempted to answer the question about whether CTG monitoring is the better approach for preventing death, including stillbirth, I have found no evidence to suggest that this is true.

Who needs to know this and what needs to happen?

The first group of people who need to take this evidence on board are maternity professionals. This group have an ethical obligation to not mislead women about the benefits of CTG use (Sartwelle et al., 2020a). Suggesting that using intermittent intermittent auscultation increases the chance the baby will die is unethical, and should not happen.

The second group of people who need to know and use this information are academics who conduct fetal monitoring research, and who educate health professionals. Not knowing, or knowing and misrepresenting the evidence is not consistent with ethical publishing or educational standards.

Finally, the other group of people who need this information are those who do medical legal work. It beggars belief that “experts” continue to provide medicolegal reports claiming that CTG use would have avoided death, as there is no evidence to suggest that this is true. There is discussion in legal circles that CTG data should not be admissible as legal evidence as it is “junk science” (Politi et al., 2023; Sartwelle et al., 2020b).

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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

Grant, A., O’Brien, N., Joy, M. T., Hennessy, E., & MacDonald, D. (1989, Nov 25). Cerebral palsy among children born during the Dublin randomised trial of intrapartum monitoring. Lancet, 2(8674), 1233-1236. https://doi.org/10.1016/s0140-6736(89)91848-5

Haverkamp, A.D., Orleans, M., Langendoerfer, S., McFee, J.G., Murphy, J., & Thompson, H.E. (1979). A controlled trial of the differential effects of intrapartum fetal monitoring. American Journal of Obstetrics and Gynecology, 134(4), 399-412.

Haverkamp, A.D., Thompson, H.E., McFee, J.G., & Cetrulo, C. (1976). The evaluation of continuous fetal heart rate monitoring in high-risk pregnancy. American Journal of Obstetrics and Gynecology, 125(3), 310-320.

Heelan-Fancher, L., Shi, L., Zhang, Y., Cai, Y., Nawai, A., & Leveille, S. (2019, Feb 27). Impact of continuous electronic fetal monitoring on birth outcomes in low-risk pregnancies. Birth, 46(2), 311-317. https://doi.org/10.1111/birt.12422

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 and Gynecology, 131(5), 526-532.

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.

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 and Gynecology 69(5), 687-695.

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 and 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 and Obstetrics, 94(2), 123-125.

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, and Reproductive Biology, 23(1-2), 1-11.

Politi, S., Mastroroberto, L., & Ghi, T. (2023, Mar 4). The time has come for a paradigm shift in obstetrics’ medico-legal litigations. European Journal of Obstetrics & Gynecology and Reproductive Biology, 284, 1-4. https://doi.org/10.1016/j.ejogrb.2023.02.018

Renou, P., Chang, A., Anderson, I., & Wood, C. (1976). Controlled trial of fetal intensive care. American Journal of Obstetrics and Gynecology, 126(4), 470-476.

Sartwelle, T. P., Johnston, J. C., Arda, B., & Zebenigus, M. (2020a). Cerebral palsy litigation after fifty years: A hoax on you. Indian Journal of Medical Ethics, V(4), 1-15. https://doi.org/10.20529/ijme.2020.093

Sartwelle, T. P., Johnston, J. C., Arda, B., & Zebenigus, M. (2020b). Electronic fetal monitoring in the twenty-first century: Language, logic and Lewis Carroll. Clinical Ethics, 16(3), 213-221. https://doi.org/10.1177/1477750920971800

Shy, K.K., Larson, E.B., & Luthy, D.A. (1987). Evaluating a new technology: the effectiveness of electronic fetal heart rate monitoring. Annual Review of Public Health 8(1), 165-190.

Small, K. A., Sidebotham, M., Fenwick, J., & Gamble, J. (2020, Sept). Intrapartum cardiotocograph monitoring and perinatal outcomes for women at risk: Literature review. Women & Birth, 33(5), 411-418. https://doi.org/10.1016/j.wombi.2019.10.002

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 and Gynecology, 81(6), 899-907.

Wood, C., Renou, P., Oats, J.J.N., Farrell, E.-M.E., Beischer, N., & Anderson, I. (1981). A controlled trial of fetal heart rate monitoring in a low-risk obstetric population. American Journal of Obstetrics and Gynecology, 141(5), 527-534.