Tissue encapsulation of the proximal Essure micro-insert from the uterine cavity following hysteroscopic sterilization.

Study Objective: To assess the interaction between the trailing ends of a sterilization micro-insert extending into the uterine cavity and the surrounding uterine tissue environment over time.

Design: Multicenter, retrospective observational study (Canadian Task Force classification II-1).

Setting: Hospital-based clinical research centers.

Patients: A subset of a study population of 545 women who had undergone a hysteroscopic sterilization procedure.

Intervention: A second-look hysteroscopy was performed in 22 (20 with uterine bleeding, 2 pre IVF) of these 545 women between 4 and 43 months from the sterilization procedure.

Measurements And Main Results: Over a mean time period of 19.73 months, the trailing coils of the micro-inserts into the uterine cavity shortened from a mean of 5.7 mm to 2.0 mm and from 5.4 mm to 1.8 mm on the right and left sides, respectively. In cases observed within 12 months or fewer post-procedure, the complete tissue encapsulation of both micro-inserts had already occurred in 17% of the observations. Among cases evaluated from 13 to 43 months post-procedure, 25% evidenced complete encapsulation.

Conclusion: Two mechanisms appear to be responsible for this process. First, there is an initial mechanical "winding-in" of the micro-insert of approximately 1 rotation of its outer coil, accounting for 1 mm of its length, after release from its delivery system. Second, the tissue around the ostium appears to use the trailing coils of the micro-insert as a scaffolding structure, gradually encapsulating and excluding them from the uterine cavity. The gradual tissue exclusion of the micro-insert from the uterine cavity may make it pregnancy-compatible after in vitro fertilization and embryo transfer procedures.