Compact long-term recorder for the transabdominal foetal and maternal electrocardiogram

Foetal heart rate (FHR) monitoring is a proven means of assessing foetal he alth during the antenatal period. Currently, the only widely available inst rumentation for producing these data is based on Doppler ultrasound, a tech nology that is unsuitable for long-term use. For nearly a century, it has b een known that the foetal electrocardiogram (FECG) can be detected using el ectrodes placed on the maternal abdomen. Although these signals suggest an alternative means of FHR derivation, their use has been limited owing to pr oblems of poor signal-to-noise ratio. However, the eminent suitability of t he transabdominal FECG for long-term FHR monitoring has suggested that pers everance with the technique would be worthwhile. The paper describes the de sign, construction and use of a compact, long-term recorder of three channe ls of 24h antenatal transabdominal data. Preliminary use of the recorder in around 400 short recording sessions demonstrates that FHR records of equiv alent quality to those from Doppler ultrasound-based instruments can be ext racted from such data. The success of FHR derivation is, on average, around 65% of the recording period from around 20 weeks gestation (although this figure is reduced from around 28-32 weeks, and the success rates exhibit a wide range when individual subjects are considered). These results demonstr ate that the technique offers, not only a means of acquiring long-term FHR data that are problematic to obtain by other means, but also a more patient -friendly alternative to the Doppler ultrasound technique.