Monitoring of fetal heart rate and uterine activity

Abstract

In this thesis a renewed monitoring technique for fetal heart rate (FHR) and uterine activity has been investigated. Through non-invasive measurements of electrical signals as recorded from the maternal abdomen, both the fetal-electrocardiogram (fECG) and uterine electrohysterogram (EHG) can be filtered for calculation of FHR and uterine contractions, respectively. This monitoring technique has been known for over 100 years, however due to technical difficulties clinical implementation has not yet been feasible. Recently, thanks to technical improvements, both fECG - and EHG monitoring have experienced a renewed surge of interest. Moreover, the use of fECG - and EHG signals yield more information compared to FHR and uterine activity as acquired with conventional monitoring techniques. For example, the high resolution characteristics of current fECG-monitors offers true beat-to-beat FHR, enabling more specific assessment of the fetal condition in complicated pregnancies. EHG-monitoring holds the promise that it might discriminate between efficient and inefficient contractions, by using power density spectral analysis. Therefore the aims of part I of this thesis were to validate FHR monitoring using the fetal ECG signal and to study the fetal condition in pregnancies complicated by intra uterine growth restriction (IUGR) and (pre)gestational diabetes . The aims of part II of this thesis were to validate monitoring of uterine contractions using EHG during labour by comparing it to the method of reference, intrauterine pressure recording (IUP), and to study whether non-invasive monitoring of uterine activity using EHG may help to differentiate between normal and dysfunctional term labour in nulliparous women. Our studies using fECG have shown that: True beat-to-beat recordings can be obtained throughout pregnancy, also in obese women. Recordings of long duration are feasible during night time when women are asleep. And some promising observations have been made in IUGR fetuses. This indicates that there will be place for this innovative technique. This will hold especially for monitoring of the IUGR fetus and fetuses of women with diabetes, although this has to be substantiated in larger series. Moreover, fECG monitoring is truly non-invasive, again in contrast to conventional Doppler recording. For EHG we conclude that, while still having to standardize the technique, it is now considered accurate for recording of contractions during labour. Moreover, our preliminary results and those of other study groups are encouraging regarding a clinically relevant role in the understanding of dysfunctional labour