The journal Ultrasound in Obstetrics and Gynecology published two papers back to back recently. Both are from the same research team based in the Netherlands, and both examined the relationship between use of epidural pain relief during labour and the use of unplanned, in labour, caesarean section or instrumental birth for “presumed fetal compromise”. The research differed in the approach used. Together, the papers raise concern that epidural use might not be as safe for the fetus as is commonly suggested. They also potentially missed an important point.
Paper number one
The first of the two papers (Damhuis, et al., 2023) drew information from national birth records. They included information from 629,951 women, who gave birth to one baby between 36 and 42 weeks of gestation. 19% of this population used epidural analgesia, 14% used some other form of analgesia (this included sedatives, opioids like morphine, and non-opioids), and the remaining 67% used no analgesia. Women who used more than one form of analgesia were not included in the study. The only definition given for “presumed fetal compromise” in the paper was that it was as decided by the care provider – I presume it relates to abnormal fetal heart rate patterns. The authors used the term “emergency delivery” to mean either caesarean section or instrumental birth performed during labour.
Women who used an epidural for pain management during labour gave birth by “emergency delivery” for “presumed fetal compromise” 13% of the time compared with 4% of women who used no analgesia (RR 3.23, 95%CI 3.16 – 3.31) and 7% of the time for women who used another form of analgesia (RR 1.72, 95%CI 1.67-1.77). Both of these differences were statistically significant. The authors then looked for factors other than the use of epidural analgesia that might have explained what was going on and mathematically corrected for these confounding variables. There continued to be a significantly higher rate of “emergency delivery” for fetal compromise in women who used epidurals, and this was true both for women giving birth for the first time and for women who had given birth before.
Neonatal outcomes were also different – with higher rates of low Apgar scores (1.9% vs 0.7%) and admission to the nursery (3.7% vs 1.3%) for women using an epidural compared to women who used no analgesia. Perinatal mortality (stillbirth in labour plus death up to 28 days of age) was low in all groups and not significantly different (5 per 10,000 births with no analgesia, or epidural analgesia, 3 per 10,000 births with alternate analgesia).
Paper number two
The second paper (Tabernée Heijtmeijer, et al., 2023) used data already collected for a randomised controlled trial. The RAVEL trial randomly assigned women to either an epidural or to self-controlled remifentanil (a short acting opioid). Like the previous paper, all women were pregnant with one baby and gave birth between 36 and 42 weeks. The outcome of interest was the use of “emergency delivery” for “presumed fetal compromise”. Data from 619 women were analysed – 46% had an epidural and 54% used remifentanil.
Once again, the rate of “emergency delivery” for fetal compromise was higher for women who used an epidural (OR 1.69, 95% CI 1.01 – 2.83) – 14.8% rather than 8.3% for those who used remifentanil. Cord blood acidosis was also more common (7.5% vs 3.9%).
So what was actually going on?
The authors proposed that changes in placental function, or alternately, that prolonging the duration of second stage of labour (which was documented in their findings), were ultimately responsible for the differences in “emergency delivery” for fetal compromise seen between women using epidurals and those who did not. They did not explore the mechanism by which epidural use might reduce placental function during labour.
While both of these explanations may well be correct, there is another possibility that was not considered in either of the two papers. No where in the papers was there any description of the approach(es) to fetal heart rate monitoring used. I’m not familiar with the context of care in the Netherlands with respect to CTG use (if you are – please add a comment and share your knowledge). In many countries where CTG use is common, professional guidelines recommend CTG use for women using epidural analgesia (for example the RANZCOG guideline here in Australia). CTG use is associated with a higher rate of caesarean section for suspected fetal compromise (Alfirevic, et al., 2017). The differences reported in these studies may be due to high rates of CTG monitoring in women using epidurals and more use of intermittent auscultation in women using no, or an alternate form of, analgesia for labour.
The “taken-for-grantedness” of CTGs, presumed to be a harmless and / or effective intervention and therefore hardly worth rating a mention, is common. These two studies provide examples of the research consequences for not considering the potential impact of CTG use on outcomes.
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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
Damhuis, S. E., Groen, H., Thilaganathan, B., Ganzevoort, W., & Gordijn, S. J. (2023, Nov). Effect of intrapartum epidural analgesia on rate of emergency delivery for presumed fetal compromise: Nationwide registry-based cohort study. Ultrasound in Obstetrics & Gynecology, 62(5), 668-674. https://doi.org/10.1002/uog.26309
Royal Australian and New Zealand College of Obstetricians and Gynaecologists. (2019). Intrapartum fetal surveillance clinical guideline. 4th Edn. https://ranzcog.edu.au/statements-guidelines https://ranzcog.edu.au/statements-guidelines
Tabernee Heijtmeijer, E. S. E., Groen, H., Damhuis, S. E., Freeman, L. M., Middeldorp, J. M., Ganzevoort, W., & Gordijn, S. J. (2023, Nov). Epidural analgesia and emergency delivery for presumed fetal compromise: Post-hoc analysis of RAVEL multicenter randomized controlled trial. Ultrasound in Obstetrics & Gynecology, 62(5), 675-680. https://doi.org/10.1002/uog.26308
Categories: CTG, EFM, New research
Tags: caesarean section, epidural, instrumental birth
Birth Small Talk 
I wonder if there was a difference in women and / their environment (support etc) between women who chose to have an epidural vs those who didn’t? I wonder if those who didn’t choose to have an epidural had better support structures that helped them feel safer and therefore in less pain. Or if needing an epidural is a sign of underlying difficulties? (E.g. baby head position). I wondered if an epidural was not the trigger for more intervention but rather a sign that that women was running up against other difficulties. I don’t have any reason to suppose these things but I always like to think outside the box and its worth thinking about whether epidural is a symptom rather than a cause of a situation that is going to lead to further intervention. Perhaps there is other factors that could change interventions.. anyway just some thoughts out loud..
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One of the two studies was a randomised controlled trial were women were randomly assigned to either an epidural or to other pain management options – so there won’t have been major differences in the sort of women, their support systems, the nature of their labour etc. You are right though that these are things that can have an impact on outcomes and need to be controlled for in research.
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