Endometrial histology during use of a low-dose estrogen-desogestrel oral contraceptive with a reduced hormone-free interval.

The object of the study was to determine the effect of a new low-dose ethinyl estradiol-desogestrel oral contraceptive on endometrial histology. The oral contraceptive regimen contained fixed doses of ethinyl estradiol (20 micrograms) and desogestrel (150 micrograms) for days 1-21, placebo on days 22 and 23, and ethinyl estradiol alone (10 micrograms) on days 24-28. Endometrial histology was assessed in tissue samples obtained during treatment cycles 13 and 14. All endometrial samples were sent to a central laboratory for processing and evaluation. No endometrial hyperplasia or metaplasia was found in the endometrial biopsy specimens obtained during cycles 13 and 14 in a subset of 12 women participating in a multicenter efficacy and safety study. These results suggest that this oral contraceptive regimen, which includes 5 days of unopposed ethinyl estradiol, is not associated with endometrial hyperplasia or metaplasia. The endometrial histologic findings observed in this study were similar to those observed during the use of 21-day combination oral contraceptive regimens.