Factors affecting the spontaneous expulsion of the levonorgestrel-releasing intrauterine system.

Objective: To estimate the incidence of, and identify risk factors for, spontaneous expulsion of the levonorgestrel-releasing intrauterine system (LNG-IUS).

Methods: Pre-insertion characteristics for 481 women who received the LNG-IUS at a single institution in the Republic of Korea between 2003 and 2011 were analyzed retrospectively. The median duration of follow-up was 13.4 months. Kaplan-Meier plots were constructed to estimate the time to occurrence of spontaneous expulsion in multiple subgroups.

Results: The overall crude incidence of spontaneous LNG-IUS expulsion was 9.6%. The cumulative incidence was 7.9%, 9.1%, and 9.6% at 1, 2, and 3 years, respectively. It was significantly higher in women with adenomyosis (9.1%, 10.6%, and 11.1%) or uterine leiomyoma (14.5%, 15.8%, and 15.8%) than in those with a normal uterus (3.6%, 4.1%, and 4.6%) (P=0.008). Women with heavy menstrual bleeding (11.0%, 12.7%, and 13.4%), dysmenorrhea (8.1%, 9.0%, and 10.0%), or pre-insertion receipt of gonadotropin-releasing hormone agonists (13.3%, 16.0%, and 17.3%) also had higher cumulative incidences than those without these conditions (P<0.05). Most (84.5%) women with a spontaneous expulsion chose to discontinue the device.

Conclusion: Clinicians need to be aware of the risk factors for spontaneous LNG-IUS expulsion because this can lead to a discontinuation of its use.