Ovarian function during low-dose oral contraceptive use.

Lowering the total steroid dose in modern oral contraceptives (OCs) has been connected with a higher incidence of ovarian follicle and cyst formation. To investigate the presence of ovarian follicles and cysts by means of vaginal ultrasonography and serum hormone determinations during use of two low-dose OCs, 65 volunteers were randomized to receive either 20 micrograms ethinylestradiol (EE) + 150 micrograms desogestrel (group A) or 35 micrograms EE + 250 micrograms norgestimate (group B) for a 2-month study period. At baseline, 39% of women in group A and 31% in group B exhibited at least one follicle < 35 mm in diameter. By the end of the second treatment cycle, the frequency of these follicles had decreased to 14% in each group. Only one subject in the higher estrogen group developed an ovarian cyst > 35 mm. One subject in each group demonstrated hormone levels characteristic of ovulation; no pregnancy occurred in either group. The 20 micrograms EE preparation was not found to lead more often to ovarian follicles or cysts when compared with a 35 micrograms EE preparation, possibly because of the type and dose of the progestogen used.