A Pilot Study on Fetal Heart Rate Extraction from Wearable Abdominal Inertial Sensors

This work proposes a novel approach for detecting fetal heart rate (FHR) using seismo-cardiogram (SCG) and gyro-cardiogram (GCG) recordings collected from abdominal inertial sensors. A proof-of-concept setup with commercially available sensor nodes is prepared. The FHR components are extracted from the fused cepstrum of recordings of all the sensors. The feasibility of the proposed method is evaluated with experiments on ten pregnant women under supine, seated, and standing positions. The results are compared with simultaneously-collected recordings of fetal cardiotocography (fCTG). The best position for collecting the signals is deemed to be the supine position, which reports best average root mean square error (RMSE) of 9.83 BPM and average positive percent agreement (PPA) of 84.44% for the SCG signal. The overall results of RMSE are 11.40 BPM from SCG and 12.08 BPM from GCG. The overall reliability from SCG is 75.02%, which is slightly lower than the value of 75.52% from GCG. In summary, the results are comparable between the two modalities, suggesting no significant difference between the usage of the two methods. Our results indicate that wearable inertial sensors could potentially be used to extract FHR outside the clinic with accuracy and reliability metrics comparable to other modalities such as fCTG.