 The fetal heart rate FHR is commonly monitored during labor to detect early fetal acidosis. FHR variability is traditionally investigated using Fourier transform, however, fetal conditions differ from adults higher frequency, widely instable signal modifying spectrum repartition along frequencies, making this approach inappropriate. New mathematic approach, including Multifractal analysis, adaptative multiscale complexity analysis, nearest-neighbor based wavelet entropy rate measures, scattering transform, may identify parameters associated with fetal acidosis. Modern classification system, driven by the data, based on these relevant parameters should help to dsiccriminate the fetus at risk for acidosis and help the clinician in decision making for the management and termination of labor. Analysing 20 to 30 minutes sliding windows with these different methods in a limited number of cases foetus born with acidosis and controls foetus without acidosis should lead to identify relevant parameters, which will be submitted to these classification tools. For external validation, a large database, including more than 4500 FHR recording documented with foetal outcomes, will be used to evaluate the performance of the combination of parameters identify and classification system used to discriminate foetuses at risk for short term acidosis or not, in order to give a relevant information to the clinician before acidosis occurs, to make the appropriate decision. 