2nd Edition of the Public Health and Midwifery World Conference 2026

Abstract

Despite its ubiquitous use, conventional cardiotocography (CTG) for intrapartum fetal monitoring has high inter-observer variability and a significant false-positive rate for fetal acidosis, contributing to an increased rate of operative vaginal deliveries and cesarean sections without a commensurate decline in cerebral palsy rates. ST-segment analysis (STAN) was developed as an adjunctive technology to improve the specificity of fetal monitoring by detecting myocardial ischemic responses to hypoxia. However, its clinical utility remains a topic of debate in obstetric practice.

Objective: This narrative review critically evaluates the evidence base for STAN technology as an adjunct to CTG. It aims to assess its physiological principles, its impact on metabolic acidosis at birth and rates of hypoxic-ischemic encephalopathy (HIE), and the clinical factors influencing its successful implementation.

Methods: A targeted literature search was performed in MEDLINE and the Cochrane Library. Keywords included "STAN analysis," "fetal ECG," "intrapartum fetal monitoring," "metabolic acidosis," and "hypoxic-ischemic encephalopathy." Large randomized controlled trials (RCTs), subsequent meta-analyses, and observational cohort studies evaluating STAN versus conventional CTG were reviewed.

Results: Early pilot studies and initial RCTs suggested that STAN guidance could reduce operative interventions for non-reassuring fetal status and decrease the incidence of moderate metabolic acidosis. However, subsequent larger trials and more recent meta-analyses have failed to demonstrate a significant reduction in the primary outcome of metabolic acidosis or HIE when compared with CTG alone. The narrative synthesis identifies critical confounding factors: (1) the prerequisite for high-quality CTG interpretation as a gateway to STAN analysis, (2) the importance of strict adherence to clinical guidelines for intervention, and (3) the challenges in adequately powering studies to detect a difference in rare outcomes like HIE. Furthermore, the widespread adoption of alternative fetal wellbeing assessments (e.g., fetal scalp lactate sampling) has shifted the clinical landscape.

Conclusion: While physiologically sound, the adjunctive benefit of STAN over high-quality CTG combined with scalp sampling has not been definitively proven in large-scale pragmatic trials. Its role may be most relevant as a second-line tool in specific high-risk populations or as a continuous monitoring method when intermittent auscultation or scalp sampling is impractical. The future of intrapartum monitoring likely lies in artificial intelligence-driven CTG interpretation rather than isolated ECG analysis.