A.P. Kazantsev - Ph.D.(Eng.), Head of Biomedical Developments, Institute for Biological Instrumentation, Russian Academy of Science (RAS), c. Pushchino
Yu.N. Ponomareva - Dr.Sc. (Med.), Professor, Department «Obstetrics and gynecology» medical faculty, State Budget Educational Institution of Higher Professional Education (SBEI HPE) «Moscow State Medical and Dental University n.a. A.I. Evdokimov» Russian Ministry of Health
A.V. Shulyakov - Senior Lecturer, Department «Information-Measuring and Biomedical Engineering», Ryazan State Radio Engineering University

Basing on the short-term Fourier transform, a fetal heart rate (FHR) measurement method that has been developed by the authors allows us to make use of aposteriory entropy for the FHR variation within a short duration analysis window. A Doppler ultrasonography signal received from a fetus-s heart is the integrated carrier of information on blood circulation in a fetal heart. A volume blood flow velocity simulation calculated from a Doppler probe audio signal is introduced. The simulation suggests better noise immunity in comparison to using a simple envelope signal that is common approach in cardiotocography. The description is given for algorithms and procedures that were implemented for computation of FHR, entropy, and Dawes/Redman-s STV. An approach to estimation and interpretation of FHR short term variability with entropy is outlined basing on real data processing. The principal results are as follows: 1. A Doppler ultrasonography oriented simulation of fetal heart blood flow variation improving noise immunity is proposed. 2. Advances of aposteriory entropy against Dawes/Redman-s STV in terms of sensitivity and time resolution are shown.