PSAFE: Extraction of Faint Fetal PPG from Non-Invasively Acquired Mixed PPG Signals

Tailai Lihe, Weitai Qian, Begum Kasap, Soheil Ghiasi

Confirmation: I have read and agree with the IEEE BSN 2025 conference submission's policy on behalf of myself and my co-authors.

Keywords: Fetal Photoplethysmography, Phase Synchronized Averaging, Transabdominal Fetal Pulse Oximetry

Abstract: Traditional approaches to intrapartum fetal monitoring, based on interpretation of fetal heart rate (FHR) tracings, have high false positive rates for detection of fetuses at risk of birth asphyxia. Transabdominal Fetal Pulse Oximetry (TFO) promises to supplement FHR trace interpretation through non-invasive sensing of fetal blood oxygen saturation (fSpO$_2$) from photoplethysmography (PPG) signals acquired through the maternal abdomen. However, the acquired signals, referred to as mixed PPG, contain contributions from both maternal superficial tissue layers and fetal tissue, as well as other noise sources. We propose Phase-Synchronized Averaging for Fetal Signal Enhancement (PSAFE), a novel algorithm that leverages fetal heart phase information to align and average mixed PPG segments. Evaluation using in-vivo data collected from pregnant ewe models demonstrate that PSAFE yielded a 43.4\% reduction in mean absolute error, and a 25.9\% improvement in correlation for fSpO$_2$ estimation, compared to a leading alternative approach.

Track: 3. Signal processing, machine learning, deep learning, and decision-support algorithms for digital and computational health

NominateReviewer:

Weitai Qian
[e-mail]

Submission Number: 42