An investigation of changes in the neonatal electrocardiogram (ECG) and respiration signals from labelled seizure data for five neonatal patient records is reported. A decrease during seizure of 5.70% in the mean RR-interval was found. The mean respiration rate per epoch was found to decrease by a mean 18.44% during seizure. No significant change in the RR-interval standard deviation or in the mean respiration amplitude during seizure was observed. These results raise the possibility of using ECG and respiration based methods instead of existing electrcoenceplogram (EEG) based methods, or in concert with EEG-based neonatal seizure detection methods to improve on previously reported seizure detection methods. © International Federation for Medical and Biological Engineering 2006.