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

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Abstract
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 days 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.