Background Ductus venosus spectral waveform has two peaks and two nadirs: S, v, D and a velocities, which are obtained after to some extent of accelerations or decelerations throughout a cardiac cycle. It is aimed to define the actual celeration times and indexes and their relationships with the fetal heart rate (FHR). Methods The acceleration times and indexes were measured in 357 patients between 11 and 40 weeks of pregnancies with low risk. Results The FHR has a gradual increasing negative correlation from time for S to time for a with each of the cardiac times of phases according to the statistical analysis (correlations were minus 190, 269, 407 and 541 for S, v, D and a phase times, respectively). The acceleration aS and the deceleration Da have positive correlations with the FHR; however, the deceleration Sv and the acceleration vD do not correlate with the FHR. Conclusion The deceleration Da time and index are the main components for determining the FHR in fetuses. Therefore, the atrial contraction is the strongest component for determining the FHR in fetuses.