Development of clinical guidelines based on fetal physiology for CTG and ST Analysis

The current clinical guidelines for CTG and ST Analysis by Neoventa are based on the FIGO guidelines from 1987. ST Analysis is always used as an adjunct to CTG and the guidelines include CTG classification and instructions on how to respond to STAN events. Following several years of clinical experience, the guidelines were amended in 2007 to include more detailed information about clinical management. The amendments were based on input from the European Expert Group on ST Waveform Analysis for Intrapartum Surveillance.

Different guidelines for CTG classification have been presented by different organisations at both national and international level. The problem with conflicting guidelines for CTG interpretation and classification is well known, as is the problem with inter-observer variability in the classification of a CTG trace. Since the introduction of CTG, the levels of HIE (Hypoxic Ischemic Encephalopathy) have not decreased whereas caesarean section rates are increasing. The challenge that obstetric staff face is that underclassification may lead to incidents of hypoxia whereas overclassification leads to unnecessary interventions.

There is growing interest in the field of obstetrics for a physiological approach to CTG interpretation and how knowledge about fetal physiology and fetal stress responses can improve clinical management and outcomes. The physiological approach goes hand in hand with ST Analysis, which provides unique information about the state of the individual fetus and its oxygenation.

new clinical guidelines

In an attempt to address the problem of conflicting guidelines and to simplify decision making, Susana Pereira, Consultant in Obstetrics and Fetal Medicine, Kingston Hospital NHS Foundation Trust, London, UK, initiated a project to investigate how new clinical guidelines, based on fetal physiology, could be developed for CTG and ST Analysis. Central to the new guidelines were simplicity of use and individualised care for the fetus.

Together with Karl G. Rosen, Professor of Perinatal Applied Physiology and Founder of ST Analysis, she conducted a study – How is the fetus? – at Kingston University Hospital where the new clinical guidelines were tested. The aim of the study was to determine the performance of the new guidelines when used by a group of obstetricians and midwives with varying degrees of experience in CTG interpretation and STAN use. The study included the classification of 54 clinical cases from all over the world. Susana Pereira recently presented the promising results of the study at the BIRTH Congress.

Susana Pereira also wanted to apply the latest knowledge within decision theory and reached out to Prof. Gerd Gigerenzer, a German psychologist who has studied the use of bounded rationality and heuristics in decision making. This resulted in the design of a new decision-making process to be used together with the new clinical guidelines. The decision-making process was inspired by a model called fast and frugal trees – a classification and decision tree with a simple graphical structure for easy interpretation.

The next step in the process is to clinically validate the new guidelines. This work is currently being performed by Susana Pereira and her team at Kingston University Hospital.

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