Endometrial morphology and bleeding patterns in Mirena® users

Endometrial morphology and bleeding patterns in Mirena® users

F. Martinez (1), F Tresserra (2)

Department of Obstetrics and Gynaecology (1); Department of Pathology,

Institut Universitari Dexeus, Barcelona, Spain (2)

Introduction: Mirena® is a levonorgestrel releasing intrauterine

system of widespread use. Although highly effective in reducing uterine bleeding,

intermenstrual or irregular bleeding is still present in some women. The

underlying mechanism are poorly understood. This study aims to evaluate

endometrial morphology changes associated with this device and its relation, if

any, with the bleeding pattern among Mirena® users for contraceptive purposes.

Methods: Mirena® users for contraceptive purposes for longer than 6

months, that kept a menstrual calendar, were ask to agree to endometrial biopsy.

Results: Forty nine endometrial biopsies were performed. Mean age of

women was 38.16+5.78 years. Mean duration of Mirena® use was 14.5+10.5

months According to bleeding pattern, 16 (32.7%) women showed amenorrea, 6 (12%)

infrequent bleeding, 13 (26.5%) regular bleeding, 8 (18.4%) prolonged bleeding,

and 5 (10.2%) irregular bleeding/spotting. In four cases the biopsy was failed

in the other 45 cases, histological features were stromal decidualization in 43

(95.6%), endometrial atrophy in 37 (82.2%), Inflammatory cell infiltrate in 17

(34.7%), fibrin deposits in 19 (41.3%) and gland dilatation in 9 (20%). No

correlation was observed when histological features or duration of treatment

were compared with bleeding pattern. When duration of treatment was compared

with histological features, only statistically significant differences were

found in glandular dilatation, those patients with longer use showed more

frequently glandular dilatation.

Conclusions: Since no correlation has been found between bleeding

pattern and histological features, other mechanisms may be involved in bleeding

during Mirena® use.

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