Cardiac Autonomic and Anxiety Regulation Via Closed-loop nEurofeedback in Recurrent Pregnancy Loss

The goal of this clinical trial is to learn whether right dorsolateral prefrontal cortex (right DLPFC)-targeted fNIRS-BCI online closed-loop neurofeedback, delivered with slow-wave acoustic cueing, can reduce anxiety symptoms and improve cardiac autonomic regulation in women with recurrent pregnancy loss (RPL) and comorbid anxiety (women aged 18-45 years, right-handed, currently not pregnant or in a missed miscarriage state). The main questions it aims to answer are: Does real neurofeedback increase the proportion of participants who achieve an anxiety treatment response (defined as ≥50% reduction in Hamilton Anxiety Rating Scale \[HAMA\] total score from baseline) compared with sham feedback, at end of treatment and at 3-month follow-up? Is the intervention safe and well tolerated, as reflected by between-group differences in adverse events during the training period? Do brain and autonomic measures show between-group differences during the first formal session, including right DLPFC HbO downregulation, interhemispheric DLPFC synchronisation, heart rate (HR), and heart rate variability (HRV) indices? Researchers will compare real right DLPFC neurofeedback to sham feedback (identical procedures and displays but weakened coupling to real-time neural activity) to see if real neurofeedback improves anxiety outcomes and brain-heart autonomic regulation. Participants will: Complete screening, baseline clinical assessments, and physical examination Be randomly assigned (1:1) to real neurofeedback or sham feedback Complete 3 days of adaptation training followed by 3 weeks of training (15 sessions; one weekday session per day; \~20 minutes each) using a block design with slow-wave acoustic cueing (1 Hz amplitude-modulated tone; 20 s rest + 40 s cueing per block; 20 blocks/session) Undergo fNIRS recording in all sessions, with ECG recorded in session 1 only (for HR/HRV analyses) Receive matched, guideline-informed cognitive-behavioural therapy (CBT) during the intervention period Complete anxiety-related assessments at baseline, \~1 hour after the final session, and 3 months after treatment, with adverse events monitored throughout the intervention period