Endometrial histology, microvascular density and caliber, and matrix metalloproteinase-3 in users of the Nestorone-releasing contraceptive implant with and without endometrial breakthrough bleeding

Abstract Objective This descriptive study evaluated endometrial histology, microvascular density and caliber, and quantification of matrix metalloproteinase (MMP-3) expression in long-term users of the Nestorone�� (NES)-releasing implant who presented or not endometrial breakthrough bleeding (BTB). Methods Endometrial biopsies were obtained from 32 healthy women with unpredictable BTB. The quantitative analysis was performed only in 20 samples. Results The mean duration of use of the implant among the 14 women with BTB was 19.6��1.0 months, and the other six women had used the implant for 17.7��2.3 months (mean��S.E.M.). Histological analysis of the endometrial tissue showed a predominance of progestogenic pattern followed by atrophic and proliferative endometrium in both groups. Mucosal breakdown and glandular pseudostratification were observed in half of the cases. Endometrial vascular density was 73.1��10.0 and 57.5��24.1 vessels/mm 2 , and maximum vessel diameter was 923.3��86.0 and 1038.0��404 ��m (mean��S.E.M.) in the group with and without BTB, respectively, without significance, and the rate of cells expressing MMP-3��1000 counted stromal cells was 155.8��24.8 and 127.0��19.0 (mean��S.E.M.) in both groups, respectively, without significance. Conclusions This study provides information about some endometrial aspects of women using NES in contraceptive implants. In addition, the endometrium was similar during long-term use of NES-releasing contraceptive implants in women with and without endometrial bleeding.