Transcutaneous Auricular Vagus Nerve Stimulation for Prevention of Postpartum Depression After Cesarean Delivery

INTERVENTION: Sham ta‐VNS group:Subjects in the sham stimulation group underwent identical operational procedures with electrodes placed over the left cymba conchae.;Ta‐VNS group:Stimulation was delivered to the left cymba conchae at a frequency of 40 Hz, with a pulse width of 300 µs, in a cyclic pattern of 30 seconds on / 30 seconds off.; CONDITION: Postpartum Depression (PPD) PRIMARY OUTCOME: Incidence of postpartum depression at 6 weeks postpartum; SECONDARY OUTCOME: Severity of PPD;Postpartum pain and cumulative consumption of opioids;Postoperative sleep quality;Overall severity of PPB; INCLUSION CRITERIA: 1. Aged between 18 and 45 years inclusive. 2. Gestational age >= 37 weeks. 3. American Society of Anesthesiologists physical status classification (ASA): Grade I–II. 4. Pre‐pregnancy body mass inde X(BMI): 20 kg/m² <= BMI <= 35 kg/m². 5. Capable of understanding the study protocol and all assessment scales, and able to communicate effectively with research staff. 6. Voluntarily participate in this study and sign the informed consent form.