In view of the unpredictable effect on ovulation, it is not surprising that irregular menstrual bleeding is the major clinical problem. The daily progestational impact on the endometrium also contributes to this problem. Patients can expect to have normal, ovulatory cycles (40%), short, irregular cycles (40%), or a total lack of cycles ranging from irregular bleeding to spotting and amenorrhea (20%). This is the major reason why women discontinue the minipill method of contraception.

Women on progestin-only contraception develop any more functional, ovarian follicular cysts. Nearly all, if not all, regress. This is not a clinical problem of any significance.

The levonorgestrel minipill may be associated with acne. The mechanism is similar to that seen with Norplant. The androgenic activity of levonorgestrel decreases the circulating levels of sex hormone binding globulin (SHBG). Therefore free steroid levels (levonorgestrel and testosterone) will be increased. This is in contrast to the action of combined oral contraception where the effect of the progestin is countered by the estrogen-induced increase in SHBG.

The incidence of the minor side effects is very little, probably at the same rate that would be encountered with a placebo.