Fetal Movement Assessment Using Optically Pumped Magnetometers from Multisensor Magnetocardiographic Recordings

Fetal movement (FM) is a key indicator of fetal health and development. Fetal magnetocardiography (fMCG) has been used to assess FM by analyzing fetal heart rate (FHR). Low-cost, non-cryogenic optically pumped magnetometers (OPMs) provide similar biomagnetic fMCG data to SQUIDs (Superconducting Quantum Interference Devices) while eliminating the need for cryogenic cooling. In this study, we used a bed-based stand-alone OPM array housed in a cylindrical three-layer shield to obtain fMCG signals. The 14-sensor OPM array operates in dual-axis mode, measuring biomagnetic fields in the y-z directions. Sensor geometry was obtained using a planar disc with dipolar coils, HALO (QuSpin Inc.). FM was computed with an algorithm that combines the magnetic field strength of the fMCG signal and the OPM sensor locations. Data were collected from four pregnant women, aged 28 to 36 weeks. fMCG signals were isolated with a projection operator algorithm, and FHR and FM were quantified. Our preliminary data demonstrate the use of OPM sensors to measure FHR and FM in a bed-based stand-alone system. FHR and FM metrics obtained in this study fall within the range reported in previous SQUID-based studies, highlighting the potential of OPM technology for fetal monitoring and research.