A phase IV, open-label, multicenter survey of 983 obstetrician-gynecologists was conducted to evaluate the incidence of
intermenstrual bleeding in 6,382 women receiving a low-dose monophasic
oral contraceptive,
ethynodiol diacetate, 1 mg, with
ethinyl estradiol, 35 micrograms (EDA 1 mg with EE 35 micrograms) over a six-month period. Most patients (75%) did not experience
intermenstrual bleeding during
therapy. Follow-up questionnaires were sent to the physicians of the 1,526 women reporting
breakthrough bleeding or
spotting; 1,027 follow-up questionnaires (67%) were returned. The questionnaires revealed that approximately one-fifth of the patients were placed on EDA 1 mg with EE 35 micrograms to regulate preexisting
bleeding; of them, 71% reported an improvement, 13% reported worsening, and 16% reported no change in their cycle regularity. Most
breakthrough bleeding or
spotting (91%) occurred in the first three months of
therapy in women with preexisting irregular
bleeding as well as in those using the
oral contraceptive solely for
birth control. Although a fair proportion of women experienced
intermenstrual bleeding, very few (5.1%) discontinued
therapy because of it. Thus, the study demonstrated that the incidence of
breakthrough bleeding and
spotting appears to be within or below the range reported for other monophasic and multiphasic
oral contraceptives. Further, in agreement with previously published reports, the data suggest that cycle control will improve after three months of
oral contraceptive use.