Cardiotocography: Is it universal? Should it be?

We wouldn’t counsel medical professionals on patient management, but you’ll have heard differences of opinion on the utility of CTG. Just to make you aware, if you haven’t been following, that there is disillusion with the overall concept (except in emergencies), but most people concede that at least it’s a tool that can be used, and that’s better than nothing. Doctors and midwives surveyed generally approve of it, but they have reservations. There are recent review articles that try to sum up clinical opinion, looking for consensus. Broadly speaking, the received wisdom these days is that CTG is at its most appropriate during labor. 

Recent correspondence in the British Medical Journal took a look at the methodology in the now-famous ‘INFANT’ study, which popular opinion considers rather damning of CTG in general. The author points out that the trial didn’t test CTG versus intermittent or no auscultation, and it had a flaw in how it handled learning in the control group. (The argument went that some clinicians have a better natural ability to read patterns.) What the INFANT trial did show was that lack of improvement in perinatal outcomes was down to management decisions, not failure to see heart rate abnormalities. So the real issue in CTG is not about CTG. Perhaps there are too many confusing false positives, or maybe there’s alarm fatigue.

There’s no such thing as a perfect study. The author continues by noting that there are frequently flaws like variations in design and interpretation frameworks, and there are distortions from intervention effect, and so on. CTG reliability is one of those things that doesn’t respond very well to statistics. The technique undeniably saves lives sometimes, when the readings are glaring. And CTG does correspond, whether that’s good or bad, with raised caesarean rates. The fact is, it’s hard to know, beyond this, exactly what its impact on the clinical landscape is. And it’s just as hard to imagine what non-invasive monitoring system could replace it.

What’s interesting is that the crisis of confidence in CTG that everyone is talking about corresponds with the big change in categorization of FHR decelerations that arose in 2007. Suddenly maternity units were calling lots more CTGs suspicious or pathological. Maybe the real fight is over changed pattern-recognition. Said another way, maybe proper CTG use is an art, not a technical skill. This was the substance of one of the studies on midwives’ and doctors’ attitudes towards CTG in labor wards since then. It was a small, semi-structured interview survey in Northern Ireland, using an assessment tool validated back in 2001. 72.5% (n = 29) of respondents viewed CTG technology positively, and 87.5% (n = 25) felt confident about their ability to interpret tracings. (60.0%, n = 24) were happy with their training so far. But their free-text answers revealed a number of professional concerns. They were of the opinion that this technology might be deskilling staff. They therefore felt that there was a need to train in alternatives to CTG.

But how to use CTG? When? New studies and review articles have emerged. One of them, with the subtitle, ‘boon or bane?’ undertook a couple years ago to assess the correlation between CTG findings, intraoperative findings, and perinatal outcomes in emergency caesarians. They were looking ultimately for predictive power in CTG for fetal distress. They noted at the outset that electronic fetal monitoring in general has become ever more common. They found, where N=271, that 90.5% of the women with suspicious and pathological CTGs had at least one peri-operative finding that might cause fetal distress or a CTG abnormality. About a third (33.7%) with abnormal CTG had normal peri-operative findings and good neonatal outcomes. Sensitivity, specificity, positive predictive value and negative predictive value of CTG for prediction of an abnormal perinatal outcome were 90.5, 66.3, 44.9, and 95.8. Conclusion? Screen with CTG only during labor. Why? Because normal CTG is more predictive of normal outcomes than abnormal CTG is of abnormal outcomes.

So the consensus is that you should be ready to use something. Which machine you use for CTG is largely a matter of what features you and your staff like. If you’re shopping with us, you might have a look at the Edan F6.

It’s got a 3-year manufacturer’s warranty, and it’s suitable for office and delivery room use. It supports American and international standards. You can get it with an optional wireless module, for the sake of portability. Maternal parameters are ECG, HR/PR, NIBP, SpO2, and temperature. 

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