Design: Prospective observational cohort study

Setting: Non-academic teaching hospital in the Netherlands

Patients or Participants: 28 patients undergoing IUD insertion

Interventions: Each patient underwent a 4-minute transvaginal ultrasound (TVUS) of the uterus in mid-sagittal section directly prior to, and directly after, IUD placement. VAS scores for pain were collected at time of placement. TVUS recordings were analysed using an automated 2D speckle tracking method for: uterine contraction frequency (CF, contractions/minute), amplitude, velocity (mm/sec), and coordination. Patients were included regardless of hormonal therapy and cycle phase. Between-subject analysis was conducted using the independent t-test and/or shapiro-wilk test, and within-subject analysis using the paired t-test. Patient VAS scores were stratified to mild and/or moderate pain (VAS below 7) and severe pain (VAS of 7 or higher).

Measurements and Main Results: Mean age was 31.6 years (SD ± 11.3), most patients were nulliparous (17/28). 17/28 patients were using oral hormonal contraception at time of IUD insertion. Mean uterine length was 67.2mm (SD ± 12.0). Median reported VAS was 7.00 (IQR 3.00). Only CF increased after IUD placement (pre-IUD 1.50 (SD ±0.35) vs. post-IUD 1.70 (SD ±0.30), p<0.001). No other UC features were affected bij IUD insertion (P>0.05). Patients with a severe VAS showed higher CF (1.64 (SD ± 0.56) vs. 1.48 (SD ±0.20), p=0.025) and a lower contraction amplitude (35.9 (SD ±3.0) vs. 25.7 (SD ±11.3)), p=0.013).

Conclusion: UC is affected bij IUD insertion, with initial analyses pointing towards (changes in) specific uterine features and patient pain experience. Namely uterine contraction frequency and amplitude difference may be most involved in pain experience associated with IUD insertion. Future studies should investigate the effect of cycle phase, parity and potential uterine pathologies on pain sensation, and confirm these findings in a larger population.