Simultaneity of foetal heart rate acceleration and foetal trunk movement determined by foetal magnetocardiogram actocardiography

We describe a new method of actocardiography, foetal magnetocardiogram (fMCG) actocardiography, which is based on the high sensitivity of the fMCG to foetal trunk movements. We demonstrate the efficacy of the method by applying it to assess the simultaneity of onset of foetal heart rate (FHR) acceleration and foetal trunk movement. The analysis was restricted to events for which the onset of FHR accelerations and foetal movements could be determined accurately, i.e. when FHR was stable and near the average quiescent level just prior to the acceleration. We found that FHR accelerations coincided with or preceded foetal movements nearly all the time. This supports the hypothesis of coordinated control of FHR accelerations and foetal movements more strongly than prior studies, based on other techniques. We also found that beat-to-beat FHR variability often decreased at or near the start of FHR accelerations and that this occurrence was an accurate marker of foetal movement onset, even when foetal movement onset lagged FHR accelerations.