RESUMEN
BACKGROUND AND OBJECTIVES: The quality of cervical mucus (CM) among the levonorgestrel-releasing intrauterine system (LNG-IUS) users is controversial. The objectives were to assess CM compared to the levels of oestradiol (E2) and the frequency of cycles with luteal activity among users of the LNG-IUS. MATERIALS AND METHODS: In total, 224 LNG-IUS users for between two months and five years were recruited at a Brazilian family planning clinic. For the cross-sectional part of the study, we enrolled 175 LNG-IUS users at 2, 6 12, 24, 36, 48, and 60 months after insertion (25 women in each group), and we performed one evaluation. For the prospective part of the study, we enrolled 49 LNG-IUS users at the same lengths of use after insertion (7 women in each group), and we evaluated these women once a week for five consecutive weeks. . RESULTS: Mean (± SEM) CM scores of all evaluations among women with single and weekly evaluations were between 3.3 ± 0.9 and 8.5 ± 0.3, respectively independently of the length of use of the LNG-IUS. Mean E2 values ranged from 45.5 ± 6.8 to 472.5 ± 34.7 pg/ml and the maximum ovarian follicle diameter on the days of evaluation varied from 14.0 ± 1.3 to 31.2 ± 0.4 mm. CONCLUSIONS: The mean CM score of all evaluations, independent of the length of use of the LNG-IUS and normal levels of serum E2, was below 10 was according to the WHO is inadequate for sperm penetration.