CTG Interpretation: study update
From pattern recognition to physiological evaluation
Hey everyone,
This month is all about intrapartum fetal monitoring. I thought I’d share the research and reviews at the top of my Zotero most accessed list. Many people consider Electronic fetal monitoring (EFM) the dumpster fire of evidence-based medicine in obstetrics. Here, we have an intervention with a false positive rate of 99% for cerebral palsy. It is used in 85% of labours in the US, and despite near-universal acceptance in developed countries, has not resulted in improved outcomes for mothers or their babies.
Here’s a tldr; if you don’t make it beyond this paragraph, download, read and share the first article below: Jia YJ et al. (2023) Pathophysiological interpretation of fetal heart rate tracings in clinical practice. It’s a delight to read and contains a framework and examples that all obstetricians should consider when approaching CTG analysis. Their group has a companion website for ready access to the framework. That link is also below.
An editorial in ANZJOG this year asked, ‘Rationalise, refine or replace?’ It referred to a systematic review in the same journal, including an analysis of 13 guidelines (Brown et al., 2023). The summary: internationally, there is near consensus on what constitutes a normal CTG; however, there is wide variation concerning the interpretation and management of abnormal ones.
Guillaume Lamé et al. (2023) asked, ‘Why is electronic fetal monitoring so hard?’ Their social scientists conducted 325 hours of interviews with staff in maternity units. They found that
EFM is a profoundly collective process involving multiple interactions between people, tasks, tools and technology, organisation, culture and behaviour, all constituting a single clinical microsystem… the work systems for EFM appear to be poorly optimised for safety… Improvement efforts focused solely on individual practice (eg, competence in CTG interpretation) are unlikely to succeed on their own.
Understandably, they found that a primary target for improvement includes interprofessional relationships on birth suites and ‘non-technical’ skills, including situational awareness, teamwork, communication, decision-making and psychological safety.
Nzelu et al. (2018) wrote about the human factors ‘Dirty Dozen in CTG misinterpretation.’
Fetal heart rate interpretation
Perhaps we can’t fix the many systems issues, so what else can we do? How do individual practitioners improve EFM interpretation and action (aside from our own - equally important - non-technical role in teams, outlined above)?
The Brown review of international EFM guidelines described how all but three of the 13 guidelines grouped CTG patterns into three distinct risk-based categories, with one using 4 (RANZCOG) and two using five categories. They stated, ‘inter-guideline variability has crucial ramifications on accuracy, safety and feasibility of CTG interpretation.’
Unfortunately, they did not address that a focus on categorisation encourages practitioners to adopt a pattern recognition approach to CTG evaluation. This flawed strategy has contributed to EFM's overall lack of effectiveness. We must move to practising and teaching a pathophysiological approach.
Each fetus has a unique reserve, compensatory response and intrauterine environment. Differing exposures to external stimuli, such as labour length, oxytocin, and non-hypoxic events, e.g., infection, will influence the CTG.
A deep understanding of fetal physiological processes enables timely recognition of the speed of onset of hypoxia, including pre-existing uteroplacental insufficiency (chronic), acute, sub-acute and gradually evolving hypoxia. Appropriate intervention will then improve perinatal outcomes.
Edwin Chandraharan and his team fully outline the above approach in their 2023 AJOG Expert Review. Like most specialists, I have read many articles and books on CTG interpretation, but given its relatively short length, this review is extremely thorough yet easy to follow. The authors report a >50% reduction in the incidence of hypoxic-ischaemic encephalopathy across 12 maternity units where the approach was introduced.
A few of the important concepts from the review follow before the files.
For more about the ZigZag pattern, see the Tarvonen M et al. (2021) review linked below.
Link to supporting website
https://physiological-ctg.com/guideline.html
Other key EFM research
I don’t think anyone has the solution to continuous fetal monitoring until we have real-time acid-base analysis. Until then, a physiological approach to FHR analysis rather than pattern recognition as part of how training is undertaken and daily conversations occur is likely part of the solution.
Cheers for now,
Danny