Length of time after insertion of the levonorgestrel-releasing intrauterine system for it to significantly alter cervical mucus quality and sperm penetration

Abstract

OBJECTIVE: To compare the qualities of cervical mucus (CM) and three parameters of sperm penetration in CM of subjects prior to insertion of levonorgestrel-releasing intrauterine system (LNG-IUS) and at 1, 3 and 5 days after insertion using WHO cervical mucus grading criteria and an in-vitro sperm penetration test (SCMPT). DESIGN: Clinically descriptive. MATERIALS AND METHODS: Twenty-five ovulatory women who desire LNG-IUS for contraception are being enrolled for participation in this study. LNG-IUS is inserted when the cervical mucus grading score (CMGS) first reaches 10. CM evaluation and in-vitro SCMPT are performed just prior to LNG-IUS insertion and on post-insertion days 1, 3 and 5. RESULTS: To date six women have completed the study. The LNG-IUS was inserted on cycle day 10 in one subject, day 12 in four subjects and day 14 in one subject when all subjects' CM was of good quality and had good sperm penetration meter scores (SPMS). There were significant decreases in the median SPMS and median CMGS among CM samples obtained just prior to LNG-IUS placement, and those obtained days 1, 3 and 5 after insertion. CONCLUSION: When the LNG-IUS was inserted at the time of maximum CM production, CM was of poor quality with poor sperm penetration by day 1 after insertion of LNG-IUS in 5 of 6 subjects and by day 3 in all six subjects and remained poor during post-insertion day 5. It appears the LNG-IUS becomes contraceptively effective 3 days after insertion, possibly earlier, however, more subjects are needed to clarify this issue. These preliminary data suggest back up contraception is not needed for more than 3 days after LNG-IUS insertion.