Endometrial effects of a 91-day extended-regimen oral contraceptive with low-dose estrogen in place of placebo.

BACKGROUND: The study was conducted to evaluate the effects of a 91-day extended-regimen oral contraceptive (OC) containing levonorgestrel (LNG) with low-dose ethinyl estradiol (EE) in place of placebo on endometrial histology. STUDY DESIGN: Endometrial biopsies were obtained prior to initiation and posttreatment, between cycle Days 60 and 84 (during combination EE/LNG tablets), between cycle Days 85 and 91 (during low-dose EE tablets) or after completion of therapy. RESULTS: Paired endometrial biopsy samples obtained before and after treatment were available for 63 subjects. Biopsy results demonstrated that this OC regimen did not promote unexpected changes in the endometrium, either during the course of active treatment with EE/LNG or during the 7-day low-dose EE interval. Endometrial hyperplasia or malignancy was not observed in any endometrial biopsy sample. CONCLUSION: Use of a 91-day extended-regimen OC with low-dose EE in place of placebo was not associated with any untoward effects on the endometrium.