Computer analysis of ultrasonic Doppler actographic signals was done in the fetal active state, resting state and during fetal breathing movement (FBM) in order to more objectively study fetal movements. 1) The amplitude and interval of movement signal spikes were analyzed in 11 voltage steps between 0.05 and 0.55V. The interval distribution showed a uniform pattern in all states when the signals were analyzed at levels below 0.10V. 2) In the fetal resting state, almost all spikes were distributed in the lowest level of amplitude. 3) In the fetal active state, the mean values for spike amplitude were high and the coefficients of variation (CV) were large. The 3-dimensional interval number histograms showed wide distribution until high amplitude and long interval steps. 4) In FBM, the mean values for spike amplitude and CV were smaller, respectively, than those in the active state and the spikes distributed in the short interval steps of 0.5-2.0 seconds. 5) The envelope processing was useful for easier recognition of fetal movement burst in the fetal active state. A very low envelope was formed in the resting state. Analyses during FBM revealed a flat but elevated envelope. The results show the possibility of automatic and objective recognition of fetal behavioral states.