While there may be a decrease in the total number of bleeding days women experience with continuous-dosed COCs (no menstrual withdrawal week), these regimens frequently result in an increased number of “breakthrough” or non-scheduled bleeding days. Breakthrough bleeding is among the main reasons cited for discontinuation of combined COCs dosed traditionally (3 weeks of active pill, 1 week of placebo) or continuously, and may offset the perceived benefit of fewer withdrawal bleeding events for many women taking continuous-dosed COCs. The exact mechanisms responsible for breakthrough bleeding patterns during hormonal contraception are unknown and may be related to the pill formulation. This study is to determine whether progestin type or estrogen dose influences bleeding patterns, side effects, or satisfaction with combined oral contraceptives (COC) dosed continuously.