The ECG has been much neglected in automatic seizure detection in the newborn. Changes in heart rate and ECG rhythm are often found in animal and adult patients with seizure. However, little is known about heart rate variability (HRV) changes in human neonate during seizure. Results of ongoing time-frequency research are presented here with the aim to compare the performance of various time-frequency distributions (TFDs) when applied to HRV time series for non-seizure and seizure newborns. The TFDs studied are the Wigner-Ville (WVD), the Spectrogram (SP), the Choi-Williams (CWD) and the Modified B (MBD) distributions. Based on our preliminary results, our current conclusion is MBD outperforms other TFDs in terms of time-frequency resolution, cross-terms suppression and to represent the newborn HRV signals of non-seizure and seizure which are closely-spaced components in the time-frequency domain.