All birth control pills contain a small amount of estrogen and progestin hormones. These hormones inhibit the body's natural cyclical hormones to prevent conception. The most spread birth control pills are combination pills.
Another kind of birth control pill that changes the number of monthly periods is progesterone-only pill( also called mini-pill). This type of birth control pill differs from others in that it contains only progesterone. It works by changing the cervical mucus. Though sometimes it affects ovulation as well. The mini-pill can be slightly less effective for pregnancy preventing.
Any type of birth control pill works better when taken every day at the same time. And it doesn’t depend on if the girl is going to have sex. With progesterone-only pills this is extremely important.
The progesterone-only pill must be taken every day without any breaks. A girl who is taking the mini-pill usually have no period at all. In other case she may expect several months without a period. To be sure that mini-pill will work properly, a girl must take it at the same time every day, not missing even one dose.
How well do birth control pills work?