This study is a single-centre randomised controlled trial. It aimed to evaluate the efficacy and safety of transcutaneous electrical nerve stimulation based on wrist-ankle acupuncture theory(TENS-WAA) combined with tramadol hydrochloride for analgesia during transvaginal ultrasound-guided oocyte retrieval, by comparing the analgesic effects and the prevention of postoperative nausea and vomiting between the TENS-WAA combined with tramadol hydrochloride group (experimental group) and the sham TENS-WAA combined with tramadol hydrochloride group (control group). Participants were randomly assigned to the experimental or control group. The experimental group received percutaneous electrical nerve stimulation based on wrist-ankle acupuncture theory 30 minutes prior to the procedure, at a frequency of 2Hz with current intensity adjusted to the maximum tolerable level.Tramadol hydrochloride 100mg was administered intramuscularly 20 minutes before surgery. The control group received sham stimulation at the lowest intensity under identical conditions. The primary outcome measure was the Visual Analogue Scale (VAS). Secondary outcome measures included skin conductance response, postoperative nausea scale, and vomiting scale.

Inclusion Criteria:

• Females aged between 21 and 42 years.
• Patients diagnosed with infertility requiring oocyte retrieval for in vitro fertilisation-embryo transfer.
• Body Mass Index (BMI) 18.5 ≤ BMI ≤ 29.9 kg/m².
• Regular menstrual cycles with ultrasound monitoring demonstrating dominant follicle development and ovulation during the natural cycle; good ovarian reserve: follicle-stimulating hormone (FSH) < 10 IU/L, antral follicle count (AFC) > 6, anti-Müllerian hormone (AMH) > 1.5 ng/ml.
• Undergoing ovarian stimulation therapy using follicle-stimulating hormone (FSH) or gonadotropin protocols.
• Electing tramadol hydrochloride injection for analgesia during oocyte retrieval.
• Voluntary participation with signed written informed consent.

Exclusion Criteria:

• History of other chronic pain conditions, or prolonged use of opioid medications, history of anaesthetic drug addiction, or chronic alcohol abuse.
• Severe pelvic adhesions.
• Presence of pacemakers or other implanted medical electronic devices.
• Concurrent use of high-frequency surgical equipment, artificial heart-lung machines, medical shortwave therapy, or microwave therapy devices.
• Presence of scarring or skin lesions at electrode application sites.
• Severe anxiety, depression, or other psychiatric conditions impairing accurate description of sensations, or any other disorders potentially affecting pain perception.
• Conditions contraindicating or affecting oocyte retrieval, such as coagulation disorders, acute pelvic inflammation, vaginitis, trichomoniasis, endometriomas, ovarian cysts.
• Individuals with laparoscopically and/or ultrasonographically confirmed endometriosis.
• Patients with ovarian hyporesponsiveness following conventional ovarian stimulation medication.

Before the trial begins, envelopes containing sequentially numbered cards from 1 to 60 will be prepared to determine participant allocation. The coordinator will open the envelopes in the order of participant enrollment. Throughout the trial, researchers are not allowed to alter the enrollment sequence. Participants will be informed in advance that they may experience electrical stimulation sensations, and communication between participants will be prohibited during the entire trial process. The statistician responsible for data analysis will remain blinded to the group allocation of participants.