Transabdominal Fetal Oximetry via Diffuse Optics: Principled Analysis and Demonstration in Pregnant Ovine Models.

Diffuse optics has the potential to offer a substantial advancement in fetal health monitoring via enabling continuous measurement of fetal blood oxygen saturation (fSpO2). Aiming to enhance the sensing accuracy and to elucidate the foundational limits of Transabdominal Fetal Oximetry (TFO) via diffuse optics, we introduce a theoretical derivation, and a comprehensive pipeline for fSpO2 estimation from non-invasively sensed diffuse light intensity values, which are leveraged to analyze datasets obtained through both simulations and in-vivo experiments in gold standard large animal model of pregnancy. We propose the Exponential Pulsation Ratio (EPR) as a key feature, and develop machine-learning models to fuse the information collected across multiple detectors. Our proposed method demonstrates a Mean Absolute Error (MAE) of 4.81% and 6.85% with a Pearson's r correlation of 0.81 (p<0.001) and 0.71 (p<0.001) for estimation of fSpO2 in simulated dataset and in-vivo dataset, respectively. Across both datasets, our method outperforms the existing approaches, enhancing the accuracy of the fSpO2 estimation and demonstrates its viability as a supplemental technology for intrapartum fetal monitoring.