Objective: In women who use oral contraceptives with low estrogen doses, a quiescent endometrium is frequently produced. Further reduction of the estrogen dose would not be expected to alter this effect. In this open-label study, the effects on the endometrium of a monophasic oral contraceptive containing 75 micrograms gestodene and 20 micrograms ethinylestradiol were assessed.
Method: Biopsies were performed on 25 women on therapy. The biopsies were performed during the late luteal phase (last 7 days) in the pretreatment cycle and during days 15-21 in cycle 6 for 13 subjects (Group A) and during days 15-21 in cycle 3 and during the late luteal phase (last 7 days) in the post-treatment cycle for 12 subjects (Group B).
Results: All subjects completed six cycles of treatment. Nine of 13 subjects pretreatment and nine of 12 subjects at cycle 3 were characterized by the pathologist as having a secretory endometrium. Four of 13 subjects at cycle 6 and ten of 11 subjects post-treatment also demonstrated a secretory endometrium. Pre-decidual changes were seen in one, two, two and zero subjects at pretreatment, after three cycles, six cycles, and post-treatment, respectively. Six subjects had an atrophic endometrium at cycle 6.
Conclusions: With monophasic gestodene/ethinylestradiol 75 micrograms/20 micrograms, a secretory or inactive endometrium was present in most subjects. Thus, the effects on the endometrium of this oral contraceptive containing a reduced estrogen dose are consistent with those produced by other low-estrogen-dose combination oral contraceptives.