Progesterone-only birth control pills (POPs), also called the "mini pill," contain progesterone instead of progesterone and estrogen which are the ingredients found in a regular birth control pill.
Estrogen-containing pills can increase the risk of clotting in women with high blood pressure, diabetes, migraine, clotting disorders and smokers. These women are encouraged to use products without estrogen. Estrogen can also decrease the production of milk in breastfeeding women. Women who want to continue to breast feed should avoid products containing estrogen.
A regular birth control pill is 93-99% effective in the first year of use and 97-99% in subsequent years of use. A progesterone-only birth control pill is effective at 97-99%.
With all birth control pills, effective pregnancy prevention relies upon the regular, daily use of the product.
Many generics are available.
The most common complaint of women using progesterone-only birth control pills is irregular periods - Not heavy bleeding, but possibly unpredictable bleeding. Most women experience lighter periods over months of use and do develop some type of pattern to their periods. Some women will experience no period after many months of taking progesterone-only birth control pills. This is not harmful. Periods will return when the pill is discontinued.