The effects of monophasic and triphasic oral contraceptives on ovarian function and endometrial thickness.

OBJECTIVE

To analyze and compare the effects of seven low-dose oral contraceptives (OCs) on ovarian function and endometrial thickness.

METHODS

Cross-sectional study of users of one of five monophasic OCs, one of two triphasic OCs and a control group of non-users. Ovarian function, endometrial thickness and serum hormone levels were monitored during days 10-12 and 16-18 of the cycle.

RESULTS

Serum estradiol was suppressed in OC users to a greater degree during days 16-18 than during days 10-12, whereas serum progesterone during 16-18 was in the anovulatory range with each preparation. Ovarian activity as measured by follicular size was lowest with desogestrel-containing OCs, whereas greater activity was seen with triphasic levonorgestrel/ethinylestradiol and triphasic norgestimate/ethinylestradiol. Endometrial thickness in OC users was significantly smaller than in controls.

CONCLUSIONS

All preparations demonstrated profound suppression of ovarian activity and effectively prevented ovulation. Ovarian suppression with desogestrel/ethinylestradiol 150/20 did not differ from that of other OCs despite its lower ethinylestradiol content. The use of both triphasic OCs, having a relatively low progestogenic activity, was associated with a higher ovarian activity than that of the monophasic OCs.