Efficacy and safety of fetal magnetocardiography for detecting fetal cardiac magnetic signals: A 2-center, single-arm, prospective clinical trial

BACKGROUND: Accurate detection of fetal cardiac time intervals is essential for diagnosing arrhythmias, yet conventional echocardiography cannot record fetal cardiac electrical activity. Fetal magnetocardiography (fMCG) offers precise, noninvasive detection, but clinical evidence remains limited. OBJECTIVE: This study aimed to evaluate the efficacy and safety of fMCG for detecting fetal cardiac magnetic signals, by comparison with fetal electrocardiography (fECG). METHODS: We conducted a 2-center, single-arm, prospective trial involving 342 pregnant women aged ≥18 years with gestational ages of >18 weeks. Each participant underwent both fECG and fMCG on the same day, with cardiac time intervals recorded. The primary end point was the detection rate of fetal cardiac waveforms reflecting atrial and ventricular rhythm relationships. RESULTS: In the full analysis set (n = 342), fMCG demonstrated a significantly higher detection rate for QRS complexes and RR intervals than fECG (87.98% vs 78.95%; P < .01), with a rate difference of 9.03% (95% confidence interval 3.50-14.56). Similar results were observed in the per-protocol set (n = 340; fMCG 87.94% vs fECG 79.41%; P < .01). Notably, only fMCG could reliably detect PR intervals (86.22%), P waves (86.22%), T waves (78.89%), and QT/corrected QT intervals (78.89%). Adverse events were rare (n = 1; 0.29%) and unrelated to the device. CONCLUSION: fMCG was superior to fECG in detecting RR and QRS signals. Moreover, fMCG uniquely enabled visualization of other intervals critical to arrhythmia diagnosis. It also exhibited a favorable safety profile, supporting its potential in fetal cardiac monitoring.