The effect of the levonorgestrel-releasing intrauterine system and the copper intrauterine device on subendometrial microvascularization and uterine artery blood flow.

Objective: To evaluate the effect of the levonorgestrel intrauterine system (LNG-IUS) and TCU 380A on the subendometrial vascularization and the uterine artery blood flow during the midluteal phase.

Design: Prospective clinical trial.

Setting: Teaching hospital.

Patient(s): The trial included 27 patients who received the LNG-IUS compared with 25 patients who received the TCU 380A.

Intervention(s): The subendometrial blood flow was evaluated using power Doppler analysis, uterine artery pulsatility index (PI), and resistance index (RI) just before inserting the intrauterine device in the midluteal phase and 3 months after.

Main Outcome Measurement(s): Power Doppler analysis, PI, RI, and endometrial thickness.

Result(s): There were no significant differences in subendometrial vascularization between the groups. Pulsatility index and RI variability (before and after) increased and endometrial thickness reduced in LNG-IUS users. We used the multiple logistic regression model to examine the potential confounding bias (age and parity). The LNG-IUS was independently associated with increased PI.

Conclusion(s): No subendometrial microvascularization difference was found between the groups. It is the first direct evidence that LNG-IUS reduced uterine artery blood flow, even after controlling for age and parity.