This randomized double-blinded control trial aims to compare the pain levels experienced by the women using the standard conscious sedation and those who had transcutaneous electrical nerve stimulation (TENS) in addition to conscious sedation. The hypothesis is that there will be less pain in women with both conscious sedation and TENS.

Women who are indicated to undergo IVF in our center will be assessed for eligibility for the study. Written consent will be obtained from those who agreed to join the study.

Eligible women recruited will be randomized according to a computer-generated randomization list prepared by a designated research staff into one of the two groups on the day of oocyte retrieval

1. Patient with both conscious sedation and active TENS
2. Patient with conscious sedation and placebo TENS

Blinding Both the women and the physician performing the procedure will be blinded from the group allocation.

Checking of effectiveness of blinding will be done by asking the patient and the physician after the procedure as to which group they think the women is in.

The procedure Women will receive ovarian stimulation according to the departmental Standard Operating Procedures. Ovarian stimulation will be monitored by ultrasound. Human chorionic gonadotrophin or an agonist (decapeptyl) will be given when the dominant follicle is at least 18mm and there are three more follicles of at least 16mm. Oocyte retrieval will then be arranged 36 hours later.

Prior to oocyte retrieval, two sets of self-adhesive electrodes will be placed on the women back on each side of the spine at T10 to S4 level. Instructions on how to titrate the TENS amplitude to the desired level that gives a strong non-painful electrical paraesthesia will be given to the women by the research nurse who is unaware of the group allocation. TENS therapy will start 5 minutes before the procedure and stop 5 minutes after the removal of oocyte aspiration needle. The TENS machine used in the study will be the Endomed 482 that delivers biphasic pulsed currents using pulse duration of 400 µs and pulse frequencies between 80-100 pulses s-. The women in the treatment group will be given a TENS machine with electrodes emitting impulses while those in the placebo group will be given a TENS machine with electrodes that is not emitting any impulses.

The woman lies on the operative bed in a lithotomy position. 25mg Pethidine and 5mg Diazepam will be given intravenously. The blood pressure and pulse of the woman are checked after the drug administration and the oxygen saturation is monitored continuously throughout the procedure. 10ml 1% lignocaine is injected to the paracervical region by the operating surgeon with a 21-gauge needle after cleansing the vagina and cervix with chlorhexidine. Under transvaginal ultrasound guidance, a 16-gauge ovum aspiration needle is introduced. Aspiration of follicles is performed with a suction pressure of 100 mmHg.

Inclusion Criteria:

• Women who undergo transvaginal oocyte retrieval

Exclusion Criteria:

• There is only one ovary
• Oocyte retrieval performed on one ovary only
• There are less than three follicles >=16mm in diameter
• Allergic to pethidine or midazolam
• Previous experience with TENS
• Skin damage or allergy at site of TENS pads application
• History of pacemaker insertion