Transcutaneous electrical nerve stimulation (TENS) for pain control during first-trimester procedural abortion: A blinded randomized controlled trial

Abstract

Objectives: To evaluate the efficacy of transcutaneous electrical nerve stimulation (TENS) to manage pain during first-trimester procedural abortion for those not eligible for or otherwise forgoing sedation.

Study design: This is a double-blinded, block-randomized superiority trial (IRB approved, NCT05320432) comparing TENS (placed posteriorly, T10-L1 and S2-S4) to sham for pain management during first-trimester procedural abortion. We enrolled pregnant people less than 12 weeks gestation, English- or Spanish-speaking at two outpatient clinics not receiving sedation. The primary outcome was self-reported pain by visual analog scale (VAS, 100 mm) with passage of largest cervical dilator. We planned to enroll 70 patients to detect a 15 mm difference in median pain score (80% power, α = 0.05).

Results: Between January 2023 and March 2024, we enrolled 70 participants. Baseline demographics were balanced between groups: median (range) gestational duration 6 (5-11) weeks, 35.7% nulliparous. Median (range) reported pain with passage of largest dilator was 44 mm (0-88) and 50 mm (0-96) in the TENS and sham groups, respectively (p = 0.56). We did not find a difference in median pain at any collected time point including placement of tenaculum, paracervical block, aspiration, or recovery. The active TENS group was more likely to say they would recommend this method of pain control to others (94 mm vs 73 mm, p = 0.01). More participants receiving TENS unit correctly identified their group allocation (91.4% vs 63.6%, p < 0.001).

Conclusion: While we did not demonstrate a difference in pain scores during the procedure, TENS is a non-pharmacologic alternative that may improve patient experience during uterine aspiration.

Implications: In a blinded randomized trial, the median pain scores during first-trimester procedure abortion did not differ between those receiving TENS or sham. However, those randomized to TENS were more likely to recommend the method. For those with contraindications to IV sedation, improved experience may justify offering TENS during first-trimester abortion care.

Keywords: Aspiration abortion; First-trimester abortion; Pain; Transcutaneous electrical nerve stimulation (TENS); VAS.