Reactivity is the pattern of reactions associated with response to changes in the environment such as stress. Labour with uterine contractions hampering fetal and uterine blood flow provides significant stress and we need to improve our ability to assess fetal reactivity biopatterns during delivery. The study illustrates progress made with regard to detailed analysis of the fetal heart rate (FHR) and beat-to-beat variations (RR-intervals) as a clinical measure of fetal reactivity. A method, named residuals, is presented of using a small set of index cases to identify parameter settings which are then further evaluated in extensive database tests of 8100 cases.