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

ObjectiveTo 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.DesignProspective clinical trial.SettingTeaching 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.