Abstract: Devices, systems and methods for monitoring of fetal health through determination of fetal heart rate are described. In an example, beat-to-beat decelerations and accelerations are monitored to estimate fetal position and orientation within the womb using magnetometer sensors. The described embodiments enable long-term monitoring that can be remote from a clinical setting, and is sufficiently portable to be operable while the mother engages in substantial motion during daily activity. An example method includes receiving, from a magnetic sensor, a combined heart signal comprising a mixture of a maternal heart signal and the fetal heart signal, estimating, based on the combined heart signal, one or more parameters associated with a location/motion of the magnetic sensor, generating a de-noised combined heart signal by performing a de-noising operation on the combined heart signal, and tracking, based on the de-noised combined heart signal, an estimate of the fetal heart signal.