ST Analysis of the Fetal ECG, as an Adjunct to Fetal Heart Rate Monitoring in Labour: A Review

Abstract

Recording the fetal heart rate has been standard practice for more than 159 years. The wooden Pinard’s stethoscope was the first technology to be introduced and its modern version is still in clinical usage in under developed countries. However, it only provides information on the number of heart beats per minute. Electronic fetal monitoring was developed with the introduction of Cardiotocography (CTG) technology, which rapidly gained clinical acceptance. It was believed that the provision of continuous information would enable clinicians to detect babies exposed to oxygen deficiency. For many years it was assumed that birth asphyxia was the principle cause of cerebral palsy [CP]. Indeed when CTG was introduced in late 1960s it was hoped that this technique would reduce the incidence of CP and mental retardation by 50 %. Unfortunately, the results showed little or no benefit with respect to long term neurological outcome, despite widespread use of the CTG. Studies have shown that 3-28% of cases of CP are associated with Intrapartum asphyxia. In a recent analysis, it has been stated that CTG will always be a nonspecific method, currently dependent heavily on subjective interpretation with large intra- and inter-observer differences. Thus the labour ward staff (and therefore the fetus) remains at risk for wrong or delayed action. To improve the scenario, recent development is invention of The STAN system (ST Analysis, Neoventa Sweden). STAN is a system for fetal surveillance that displays the FHR and information resulting from the computerised analysis of ST interval of the fetal ECG. This system is based on ECG changes determined by the myocardial adaptation to oxygen deficiency.