Birth Control Options for Women - Oral Contraception

Types of Regimens. Combination pills are sold in 21-day or 28-day packs:

Each pill in the 21-day pack contains the necessary estrogen and progestin.
The 28-day pack adds seven differently colored "reminder" pills; they are inactive and do not contain hormones, but help the user maintain her daily routine during seven days between active pill use.

OCs may be taken in cycles that include pills of the same or different strengths. These are categorized as monophasic (one-phase), biphasic (two-phase), or triphasic (three-phase).

Monophasic regimen (e.g., Alesse, Brevicon, Demulen, Desogen, Genora, Levlen, Levlite, Loestrin, Lo/Ovral, ModiCon, Necon, Nordette, Norethin, Norinyl, Ortho-Cyclen, Ortho-Novum, Ovcon, Ovral, Yasmin, Zovia.) A 21-day pack uses tablets that are one strength and one color for 21 days. (A 28-day pack adds seven inactive tablets of a different color.)
Biphasic regimen (e.g., Mircette, Necon, Nelova, Ortho-Novum). A 21-day pack consists of tablets of one strength and color taken for seven or 10 days, then a second tablet with a different strength and color for the next 11 or 14 days. (And a 28-day pack adds seven inactive tablets of a third color.)
Triphasic regimen (e.g., Cyclessa, Estrostep-21, Ortho-Novum 7/7/7, Ortho Tri-Cyclen, Tri-Levlen, Tri-Norinyl, Triphasil, Trivora). This pack consists of tablets with three different colors and strengths. In the first phase, there are tablets of one color for five to seven days; for phase two, a second color and strength tablet is taken for five to seven days; and for phase three, a third color and strength tablet is taken for five to 10 days. The difference in duration of each phase depends on the brand. (And a 28-day pack includes a fourth color inactive tablet for the last seven days.)

In all cases, women continue to menstruate, but their periods are lighter, shorter, more regular, and less painful than in women who are not on the pill. It is not clear if the biphasic or triphasic regimens offer any advantage over the monophasic in controlling bleeding. The monophasic regimen is the most studied regimen, and a major analysis found no major differences in bleeding control between monophasic and biphasic systems. One analysis found better bleeding control with the triphasic than the biphasic, but this have been due to different progestins used in each regimen (levonorgestrel in the triphasic and norethindrone in the biphasic).

Some researchers are investigating continuous oral contraceptives, either by extending a monophasic regimen or by using specific agents (. e.g., Seasonale, which contains estrogen and levonorgestrel). This approach produces a period only about every three months. Continuous OCs have the potential for helping women with either heavy bleeding, painful periods, or both. Breakthrough bleeding is the most common side effect but decreases over time. This approach is not suitable for women who frequently miss taking their pills. Long-term effects of steady hormone use are not known, and continuous contraceptives are still in trials.