Aims: Currently one of the most widespread systems for the computerized analysis of the fetal heart rate (FHR) is the Dawes-Redman system, where the short-term variation (STV) of the FHR is measured by dividing each minute into 16 segments (STV16). Technical progress has allowed for the development of a new algorithm, which measures the STV by dividing each minute into 240 segments (STV240), thus approximating the beat-to-beat variation. The STV240 still lacks reference values. Our aim was to develop clinically relevant reference values for the STV240 and compare them to the ones for the STV16.
Methods: In a single centre, observational study, a total of 228 cardiotocograms were registered and subsequently analyzed with both algorithms (STV240 and STV16).
Results: The 95% confidence interval (CI) was calculated for both algorithms. The values of the STV240 were significantly lower in comparison to the ones of the STV16. Not only the mean values but also the 95th percentile of the STV240 lay beneath the existent cut-off value for the STV16.
Conclusions: Every clinician using the new algorithm must be aware that the normal values for the STV240 lie beneath the, up until now, established cut-off values for the STV16.
Keywords: Cardiotocography; IUGR; computerized cardiotocography; short-term variation.