Review discussing the scientific evidence from the RCT:s and Meta-analyses, important differences in European and US trials and describes valuable information of the use of ST Analysis.

In this interesting review by Isis Amer-Wåhlin and Anneke Kwee are the scientific evidence from RCT:s and meta-analyses, all comparing CTG-only monitoring with CTG+ST Analysis, discussed and also the limitations of these studies. It also describes valuable information in certain situations of the use of ST Analysis.
In year 2000 ST Analysis was introduced after many years of research starting with experimental animal research. The STAN® concept is based on the association between changes of the ST-interval of the fetal ECG and the function of the fetal myocardium during hypoxia.

Randomized clinical trials
Five RCTs have been published out of six performed. All comparing CTG-only monitoring with CTG with ST Analysis.

1. Westgate et al. The first RCT showed a trend in less metabolic acidosis, decrease in operative vaginal deliveries by 46%.

2. Amer-Wåhlin et al. Performed with computerized ST Analysis and showed a significant decrease in neonatal metabolic acidosis by 53 % and operative vaginal delivery rate by 17 % .

3. Ojala et al. A decrease in FBS by 56 %.

4. Vayssiére et al. A decrease in FBS by 56 %.

5. Westerhuis et al. Decrease in umbilical artery metabolic acidosis in blood by 39 % and FBS by 48 %.

Six published meta-analyses showed that CTG + ST-analysis reduced the risks of vaginal operative delivery by about 10% and fetal blood sampling by 40%.

There are conflicting results regarding the effect on metabolic acidosis, much because of controversies about which RCTs should be included in a meta-analysis, and because of differences in methodology, execution and quality of the meta-analyses.

Cohort studies
Several cohort studies have been published, some showing significant decrease of metabolic acidosis after the introduction of ST-analysis. Two observational studies from Sweden and Norway are describing a higher use of the STAN technology with a result of very low metabolic acidosis rate. Clinicians become more comfortable in using tool and the may improve the results of STAN.

ST-analysis has been extensively studied and the results are clashing. Most meta-analyses show that the use of ST-analysis does not reduce the incidence of metabolic acidosis, but reduce the incidence of operative vaginal deliveries and the need for FBS. The opinions related to the published evidence in terms of interpretation of studies announces a doubt if evidence of fetal monitoring will ever be black or white maybe when a known long-term outcome is published. There are promising cohort studies showing a decrease of metabolic acidosis over time. In labor ward, the cohort studies are possibly reflecting the situation over time in a better way than that of an RCT.

In conclusion, ST-analysis is effective in reducing operative vaginal deliveries and fetal blood sampling but the effect on neonatal metabolic acidosis is still under debate.

Abstract – Amer-Wahlin and Kwee

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