Subjects will be screened over the phone or in Tufts GYN clinic for participation in the study. If eligible and interested in participating, written informed consent (and assent if applicable) will be obtained. After informed consent/assent, the patient will be enrolled in the study. The patient will decide if they desire to use TENS unit during IUD insertion appointment and inform the study team. The clinic visit will proceed as normal, with additional study proceedings as follows. The study personnel will complete the 'Background Questionnaire' with the patient prior to IUD insertion. During the IUD insertion appointment, study personnel will assist in collection of the 'Study visit' data collection form. This includes recording the patient's pain score at various time points throughout the insertion procedure:

• anticipated pain during IUD insertion
• baseline pain prior to insertion
• speculum insertion
• tenaculum placement
• paracervical block administration (if performed)
• cervical dilation (if performed)
• uterine sounding
• IUD insertion
• 5 minutes after IUD insertion

Study personnel will also time the insertion procedure and collect additional data as outlined in the 'Study visit data collection form.' After IUD insertion, the participant will be asked to complete the 'Post-IUD Insertion Survey.' Once this survey is complete, this will conclude the study participation. Participation will last through the study visit only.

As part of the standard of care, a urine pregnancy test will be obtained and confirmed negative prior to IUD insertion. Patients will receive routine pain management modalities per shared decision-making with their clinical provider which may include NSAID administration, paracervical block, and heating pad.

Inclusion Criteria:

1. Persons with a uterus desiring insertion of intrauterine device
2. Able to provide informed consent/assent
3. Age 12-50 years old
4. Minors 12 years of age and older will be included in the study if postmenarchal

Exclusion Criteria:

1. Unable to provide informed consent/assent

2. Prior cervical procedure (ie loop electrosurgical excision procedure, LEEP)

3. Concurrent cervical or intrauterine procedure (ie colposcopy or dilation and curettage)

4. Cutaneous damage at the TENS electrode sites

5. Chronic or pre-procedure use of opioids

6. Chronic pain diagnosis

7. Prior IUD insertion

8. Any contraindication to intrauterine device (IUD):

   1. Pregnancy
   2. Uterine anomaly that distorts the uterine cavity
   3. Acute pelvic inflammatory disease (PID)
   4. Postpartum endometritis or infected abortion in the past 3 months
   5. Unexplained abnormal uterine bleeding
   6. Wilson's disease or copper allergy (contraindication to copper IUD only)
   7. Breast cancer (contraindication to levonorgestrel IUD only