ST waveform analysis vs. cardiotocography alone for intrapartum fetal monitoring: A systematic review and meta-analysis of randomized trials

Abstract

Introduction. ST waveform analysis was introduced to reduce metabolic acidosis at birth and avoid unnecessary operative deliveries relative to conventional cardiotocography. Our objective was to quantify the efficacy of ST waveform analysis vs. cardiotocography and assess the quality of the evidence using the Grading of Recommendations Assessment, Development and Evaluation tool. Material and methods. We identified randomized controlled trials through systematic literature searches and assessed included studies for risk of bias. Meta-analyses were performed, calculating pooled risk ratio or peto odds ratio. We performed post hoc trial sequential analyses for selected outcomes to assess the risk of false-positive results and the need for additional studies. Results. Six randomized controlled trials were included in the meta-analysis. ST waveform analysis was not associated with a reduction in operative deliveries due to fetal distress, but we observed a significantly lower rate of metabolic acidosis (peto odds ratio 0.64; 95% confidence interval 0.46–0.88). Accordingly, 401 women need to be monitored with ST waveform analysis to prevent one case of metabolic acidosis. No statistically significant effects were observed in other fetal or neonatal outcomes, except from fetal blood sampling (risk ratio 0.59; 95% confidence interval 0.45– 0.79) and a minor reduction in the number of operative vaginal deliveries for all indications (risk ratio 0.92; 95% confidence interval 0.86–0.99). The quality of the evidence was high to moderate. Conclusions. Absolute effects of ST waveform analysis were minor, and the clinical significance of the observed reduction in metabolic acidosis is questioned. There is not enough evidence to justify the use of ST waveform analysis in contemporary obstetrics. Abbreviations: CTG, cardiotocography; GRADE, The Grading of Recommendations Assessment, Development and Evaluation; MeSH, Medical Subject Headings; NICU, neonatal intensive care unit; OR, odds ratio; RCT, randomized controlled trial; RR, risk ratio; STAN, ST waveform analysis; TSA, trial sequential analyses.