Identifying newborns with umbilical cord blood metabolic acidosis by intrapartum cardiotography combined with fetal ECG ST analysis (STAN): comparison of the new and old FIGO systems to classify cardiotocograms.

The intrapartum cardiotocography (CTG) classification system by FIGO in 2015 (FIGO2015) was introduced to simplify CTG interpretation, but it is not harmonized with the fetal ECG ST analysis (STAN) algorithm from 2007 (STAN2007), which is based on the FIGO CTG system from 1987. The study aimed to determine time courses and sensitivity between the systems in classifying CTG + ST events to indicate metabolic acidosis at birth. Forty-four cases with umbilical cord artery metabolic acidosis were retrieved from a European multicenter database. CTG patterns and timing of the first occurring significant ST events were evaluated in consensus by an expert panel and sensitivity statistics were performed. Wilcoxon's matched-pairs signed-ranks test and McNemar's test were used with a two-tailed  < .05 regarded significant. STAN2007 had a higher sensitivity (73 versus 43%,  = .0002) and alarmed for metabolic acidosis in mean 34 min earlier than the FIGO2015 system did ( = .002). In every fourth case, the time difference was ≥20 min. In this simulation study, surveillance with STAN2007 combined with fetal ECG ST analysis had a significantly higher sensitivity and would have alarmed for metabolic acidosis significantly earlier than the new FIGO system would have.