STAN clinical guidelines and the new FIGO CTG classification system

In 2015 the International Federation of Gynecology and Obstetrics (FIGO) presented a new classification system for interpretation of intrapartum CTG, replacing the old system from 1987. The new system is a 3-tier classification system instead of a 4-tier, where the preterminal CTG class has been omitted. Furthermore, the definitions of tachycardia and decelerations, and time durations of abnormal variability have been changed. All this with the aim to create a simple and more objective CTG classification system.

The new FIGO system was introduced without prior studies on benefits and safety for mother and baby and this has raised questions among STAN users whether the new FIGO CTG classification system can replace the CTG system used in the STAN interpretation algorithm, which is based on the 1987 FIGO system. A recently published study shows that the old and new systems classify CTG patterns and significant ST events discrepantly and that the systems are not exchangeable in the STAN interpretation algorithm (Olofsson et al., Acta Obstetricia et Gynecologica Scandinavica, accepted 2017).

The authors in the same way evaluated a FIGO-approached new CTG classification system introduced in Sweden 2017 by the Swedish Society of Obstetrics and Gynecology, and found also for that system that it cannot interchangeably be used in the STAN interpretation algorithm.

The clinical relevance of the findings is addressed in an ongoing study, where particularly the time frames to identify significant ST events indicating neonatal metabolic acidosis are compared between the old and new CTG classification systems combined with ST analysis. The new studies will possibly lead to adjustments in STAN clinical guidelines regarding CTG classification, but no changes will be performed unless their consequences have been tested scientifically.

Neoventa Medical
Per Olofsson, Medical Advisor

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