While COCs containing 20 μg EE may be theoretically safer, this review did not focus on the rare events required to assess this hypothesis. Data from existing randomized controlled trials are inadequate to detect possible differences in contraceptive effectiveness. Low-dose estrogen COCs resulted in higher rates of bleeding pattern disruptions. However, most trials compared COCs containing different progestin types, and changes in bleeding patterns could be related to progestin type as well as estrogen dose. Higher follow-up rates are essential for meaningful interpretation of results.
A comparison of cycle control with monophasic levonorgestrel/ethinylestradiol 100 micrograms/20 micrograms versus triphasic norethindrone/ethinylestradiol 500-750-1000 micrograms/35 micrograms: a multicenter, randomized, open-label study.
This multicenter, randomized, open-label study was undertaken to compare the effects on menstrual cycle control of two oral contraceptive regimens: monophasic levonorgestrel (LNG) 100 micrograms/ethinylestradiol (EE) 20 micrograms (Alesse or Loette) and triphasic norethindrone (NET) 500-750-1000 micrograms/EE 35 micrograms (OrthoNovum 7/7/7).
                Healthy women with normal menstrual cycles were enrolled and completed up to four cycles of study medication. A total of 384 cycles in the LNG/EE group and 400 cycles in the NET/EE group were evaluable for analysis of cycle control.
                For all treatment cycles, the percentage of cycles classified as normal was consistently higher in the LNG/EE group than in the NET/EE group. By cycle 4, 69.9% of cycles with LNG/EE and 54.4% with NET/EE (p < 0.05) were normal. In individual cycles, consistently lower occurrences of intermenstrual bleeding (total bleeding and/or spotting) were seen for the LNG/EE group, although these differences were not statistically significant. Withdrawal bleeding characteristics were comparable between the two groups, except for the length of the latent period, which was significantly longer in the LNG/EE group. The incidence of treatment-emergent adverse events was similar in the two groups.
                This study indicates that the monophasic LNG/EE 100 micrograms/20 micrograms provides better cycle control than the multiphasic NET/EE product, despite its lower EE dose.