Antenatal assessment using the FECG obtained via abdominal electrodes

During the past decade a variety of intrapartum fetal monitors have been constructed that process the entire fetal electrocardiogram (FECG), obtained via a scalp electrode. They therefore differ from conventional monitors in aiming to extract relevant timing and magnitude information from the morphology of the FECG rather than simply the RR interval and hence heart rate. An intrapartum monitor such as this has been successfully developed by ourselves. This paper describes the early results obtained whilst attempting to extend this form of monitoring forward into the antenatal period. In order to achieve this the FECG must be acquired via surface electrodes placed on the maternal abdomen, which yields a signal containing the FECG amidst a number of noise sources. Our investigations into the feasibility of "antenatal abdominal FECG analysis" have been on two fronts. The first has been to produce a bedside monitor similar in function to our intrapartum device, whilst the second has been to address the possibility of performing such monitoring in ambulant subjects. At present the antenatal bedside monitor has successfully extracted and processed the FECG in approximately 75% of the cases studied, with subjects ranging from 20 weeks through to term having been monitored. We also have demonstrated the feasibility of the long term monitoring of maternal and fetal heart rate using a portable instrument.