A very-short-term intermittency of fetal heart rates and developmental milestone

We noticed that fetal heart rates (FHR) of immature fetuses intermittently showed unstable sudden and brief falls below baseline FHR that occur over a few or several heartbeats. The frightening falls do not occur in mature fetuses. In nonlinear dynamics, the degree of such abrupt falls in time series is quantified as intermittency. We aimed to investigate the nature and maturational changes of intermittency of the FHR in normal fetuses and to present the intermittency values of normal fetuses according to gestational weeks. FHR data of 450 normal fetuses between 23 and 40 wk of gestation were studied. We performed multifractal analysis and highlighted a very-short-term intermittency (C1alpha, 4