Development of a fetal and maternal heart rate recorder for ambulatory use

Two intermediate devices have been constructed to investigate the possibility of producing a fetal and maternal heart rate recorder for long-term ambulatory recording from electrodes on the maternal abdomen. The first is a solid-state recorder which uses three electrodes to record digitised abdominal signals and then download the data on to a PC through an RS232 interface. The second is a TMS32010 board on which appropriate algorithms have been developed for extracting the heart rates from the digitised signal. The design and implementation of both devices are presented together with examples of their use. A tagging scheme is incorporated to signify the degree of confidence on the extracted data. These results demonstrate that although data acquisition is compromised during vigorous movement and muscle activity, the development of a single compact portable recorder based on these two designs is feasible