Effects of the levonorgestrel intrauterine system (LNG-IUS) on cervical mucus quality and sperm penetration

Abstract

OBJECTIVE: No study has shown that changes in cervical mucus prevent sperm penetration in LNG-IUS users. The purpose of this study was to compare the depth of sperm penetration in the mid-cycle cervical mucus of LNG-IUS users to non-users with in-vitro sperm penetration tests using standardized sperm from a single donor; and by performing WHO cervical mucus grading.DESIGN: 20 LNG-IUS users and 20 controls are being enrolled in an investigator-blinded, age-matched, pharmaco-physiologic study.MATERIALS AND METHODS: Cervical mucus assessment at mid-cycle was estimated by home urinary luteinizing hormone tests. Cervical mucus was microscopically examined and graded using WHO criteria. Mucus was incubated with sperm from one standardized donor using both the Kremer Sperm Cervical Mucus Penetration Test (SCMPT) and the WHO Modified Slide Test. Depth of linear penetration of the vanguard sperm, density of penetration and forward motility were assessed microscopically and categorically graded. All parameters were dichotomized and compared using Fisher Chi-Square tests.RESULTS: To date, 46 subjects have been enrolled. Twelve LNG-IUS users and fifteen controls have completed the study. Of users, 20% had cervical mucus analysis grading over 10 (“good”) vs. 71% of controls (p=.02). WHO Modified slide test showed significantly less mucus with penetration by sperm for LNG-IUS users than controls (11% vs. 58%, p=.04). SCMPT demonstrated significantly lower “good/excellent” penetration of cervical mucus by sperm for users vs. controls at 2 and 6 hrs (0% vs. 85% at 2 h, p =.0005; 0% vs 77% at 6 h, p =.002). No cervical mucus from LNG-IUS users had good sperm penetration of mucus.CONCLUSIONS: The quality and sperm penetrability of mid-cycle cervical mucus are significantly less among LNG-IUS users than controls. The high contraceptive efficacy of the LNG-IUS occurs because the local release of levonorgestrel prevents sperm transport through the cervical mucus to the endometrial cavity, and fertilization does not occur. OBJECTIVE: No study has shown that changes in cervical mucus prevent sperm penetration in LNG-IUS users. The purpose of this study was to compare the depth of sperm penetration in the mid-cycle cervical mucus of LNG-IUS users to non-users with in-vitro sperm penetration tests using standardized sperm from a single donor; and by performing WHO cervical mucus grading. DESIGN: 20 LNG-IUS users and 20 controls are being enrolled in an investigator-blinded, age-matched, pharmaco-physiologic study. MATERIALS AND METHODS: Cervical mucus assessment at mid-cycle was estimated by home urinary luteinizing hormone tests. Cervical mucus was microscopically examined and graded using WHO criteria. Mucus was incubated with sperm from one standardized donor using both the Kremer Sperm Cervical Mucus Penetration Test (SCMPT) and the WHO Modified Slide Test. Depth of linear penetration of the vanguard sperm, density of penetration and forward motility were assessed microscopically and categorically graded. All parameters were dichotomized and compared using Fisher Chi-Square tests. RESULTS: To date, 46 subjects have been enrolled. Twelve LNG-IUS users and fifteen controls have completed the study. Of users, 20% had cervical mucus analysis grading over 10 (“good”) vs. 71% of controls (p=.02). WHO Modified slide test showed significantly less mucus with penetration by sperm for LNG-IUS users than controls (11% vs. 58%, p=.04). SCMPT demonstrated significantly lower “good/excellent” penetration of cervical mucus by sperm for users vs. controls at 2 and 6 hrs (0% vs. 85% at 2 h, p =.0005; 0% vs 77% at 6 h, p =.002). No cervical mucus from LNG-IUS users had good sperm penetration of mucus. CONCLUSIONS: The quality and sperm penetrability of mid-cycle cervical mucus are significantly less among LNG-IUS users than controls. The high contraceptive efficacy of the LNG-IUS occurs because the local release of levonorgestrel prevents sperm transport through the cervical mucus to the endometrial cavity, and fertilization does not occur.