Antenatal surveillance through estimates of the sources underlying the abdominal phonogram: a preliminary study

Abstract

Today, it is generally accepted that current methods for biophysical antenatal surveillance do not facilitate a comprehensive and reliable assessment of foetal well-being and that continuing research into alternative methods is necessary to improve antenatal monitoring procedures. In our research, attention has been paid to the abdominal phonogram, a signal that is recorded by positioning an acoustic sensor on the maternal womb and contains valuable information about foetal status, but which is hidden by maternal and environmental sources. To recover such information, previous work has used single-channel independent component analysis (SCICA) on the abdominal phonogram and successfully retrieved estimates of the foetal phonocardiogram, the maternal phonocardiogram, the maternal respirogram and noise. The availability of these estimates made it possible for the current study to focus on their evaluation as sources for antenatal surveillance purposes. To this end, the foetal heart rate (FHR), the foetal heart sounds morphology, the maternal heart rate (MHR) and the maternal breathing rate (MBR) were collected from the estimates retrieved from a dataset of 25 abdominal phonograms. Next, these parameters were compared with reference values to quantify the significance of the physiological information extracted from the estimates. As a result, it has been seen that the instantaneous FHR, the instantaneous MHR and the MBR collected from the estimates consistently followed the trends given by the reference signals, which is a promising outcome for this preliminary study. Thus, as far as this study has gone, it can be said that the independent traces retrieved by SCICA from the abdominal phonogram are likely to become valuable sources of information for well-being surveillance, both foetal and maternal.

A systematic scoping review to identify the design and assess the performance of devices for antenatal continuous fetal monitoring

“…Ten of the 43 studies were from the UK [25][26][27]35,[37][38][39]49,50,55], 22 from other European countries [24,[28][29][30][31][32][33]36,40,[42][43][44]48,[51][52][53][54]56,57,61,64,65], five from Japan [41,59,60,62,63], one from India [45], one from Australia [66], three from the United States of America (USA) [46,47,58], and one study from both the Netherlands and USA [34]. The included studies were heterogeneous, they had a median sample size of 34.5 participants (range 1-657) and a median number of recordings of 63 (range 1-657).…”

“…Two studies used only fPCG devices, of which one was named the Fetaphon-2000 [42] and the other was unnamed [45]. Three studies investigated both fECG and fPCG devices, all of which were unnamed [32,37,41]. The remaining study used a combined fECG/fPCG device named the Invu system [46].…”

“…With regard to fPCG, there were five different device designs and detection technologies. All the devices used between one and four abdominal phonocardiographic sensors, and two studies stated a specific placement of the sensors-either directly over the fetal heart [37] or in a predetermined abdominal position [41]. Furthermore, two studies securely attached the sensors to the maternal abdomen using either belts [32] or a 3-D printed plastic harness [41].…”

“…for three studies [32,37,40] for either validation or to aid signal recovery, with one study using a US-based Doppler instrument for reference purposes [45].The single combined fECG/fPCG device used a combination of electrodes and acoustic sensors, secured to the abdomen using a wireless belt, to monitor the FHR [46]. The FHR was independently detected by both methods and the signals combined to produce a reliable FHR trace.…”

“…above a certain level of quality [25,27,31,44,48,57]; traces with successful signal separation [55]; traces with successful estimation of the FHR [32,37]; or traces with successful measurement of the T/QRS ratio [30]. The success rates have a broad range (42.9-100%), and there is no obvious association between the year of the study and the success indicating no obvious improvement over time.…”