Influence of maternal and fetal factors on fetal magnetocardiography measurements using optically pumped magnetometers

BACKGROUND: Fetal magnetocardiography (fMCG) noninvasively measures the magnetic fields generated by the fetal heart to assess cardiac electrophysiology. The advent of optically pumped magnetometers (OPMs) enables portable, cryogen-free acquisition of high-fidelity fMCG signals. However, maternal and fetal characteristics may introduce variability affecting signal quality and cardiac time-interval (CTI) detectability. OBJECTIVE: This study quantifies the influence of maternal and fetal parameters (placental position, body mass index, fetal heart distance, and gestational age [GA]) on the signal-to-noise ratio (SNR) and CTI detectability in OPM-based fMCG recordings. METHODS: A total of 107 OPM recordings were obtained longitudinally from 32 pregnant participants (28-38 weeks of gestation) using a bed-based, stand-alone OPM array system. SNR was derived from fMCG signals, and maternal and fetal characteristics were obtained from clinical data. Mixed-effects linear and logistic regression models were used to evaluate associations among these parameters, SNR, and CTI detectability. RESULTS: of 19.8%. SNR increased significantly with GA and decreased with fetal heart distance. Higher SNR was associated with improved CTI detectability, particularly for T wave and QT interval. GA remained a significant predictor of T-wave detectability, whereas fetal heart distance exerted an independent negative effect. CONCLUSION: Fetal heart distance and GA are the primary determinants of OPM-fMCG signal quality. Accounting for maternal physiological variability is essential for optimizing acquisition protocols and improving the interpretability of fetal cardiac data.