It is time to introduce ST analysis for fetal monitoring in the labor ward?

After a thorough evaluation of the published data, the authors of this commentary take a definite position in favor of ST analysis in clinical practice. The basis for their standpoint is the solid fundament of experimental data revealing the importance of changes in the ST waveform of the fetal ECG for identification of intrauterine hypoxia. In addition, it is a fact that compared to the alternative of using FBS during labor, ST analysis is less invasive (only needing one perforation of the scalp), and ST information is available momentarily and continuously and thus time-saving, while FBS only gives punctual information with a delayed decision-to-result up to 18 minutes.

Five randomized controlled trials (RCT) have been published, showing an overall result of 20-30% reduction of severe arterial metabolic acidosis, a 45% reduction of the use of FBS and a 10% reduction in operative vaginal deliveries.

A clear learning curve was found in one of the larger RCTs, with increasingly better results in the ST+CTG group in the second part of the study. Obtaining enough knowledge to gain confidence in a new technology takes time and the presence of a learning curve therefore seems logical, and this is apparent in observational studies on neonatal outcome in the years following the introduction of ST analysis.

In a Swedish hospital (Mölndal), the usage of ST analysis over seven years increased from 29% to 69% while the incidence of cord artery metabolic acidosis decreased from 0.72% to 0.06%. A Norwegian hospital (Bergen) reported five-year data with an increased usage of ST from 20% to 33% of labors, and a decrease from 13 to 5 annual cases of severe metabolic acidosis in this group, while the overall incidence of cesarean deliveries fell slightly. A large London hospital (St. George’s) also reported five-year data, showing that training in CTG-interpretation and competency testing was associated with a fall in severe metabolic acidosis from 1.35% to 0.76%, neonatal death from 1.7 to 1.3/1000 and a decrease in emergency cesarean deliveries from 15% to 9%. A recent study has shown that the risk of an adverse neonatal outcome after monitoring with CTG+ST analysis was dependent on the time between an indication of hypoxia and delivery.

Several additional benefits of using the ST technology are listed (see table below) and the authors’ viewpoint is that the reported progressive improvements in outcome most likely are a result of a combination of all these factors. In addition, two different studies have shown that ST analysis is cost-effective compared to CTG alone.

The authors conclude that with a continued use and introduction of strict training programs outcome may well continue to improve, and so, it is time to introduce ST analysis in the labor ward.

Abstract – Visser and Kessler 2014

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