About birth control pills
Birth control pills are oral contraceptives that are extremely effective at preventing pregnancy. They do this by either preventing ovulation, thickening the cervical mucous, or changing the endometrial lining of the uterus. There are two main types of birth control pills: combination pills and progestin-only pills.
What do birth control pills look like?
Birth control pills come in packages that contain one month's supply of pills. They either come in 28-day packs or 21-day packs.
The 28-day packages come with three weeks worth of "active pills" and one week's worth of "inactive," or reminder, pills. The active pills are the pills that actually contain the hormones that prevent pregnancy. The only function of the inactive, or reminder pills, is to keep you on track so that you start your next pack on time.
The 21-day packages only contain active pills. When you finish the pack you must wait seven days before starting the next pack.
© - Reproduced with permission of SexInfo, University of California at Santa Barbara, 2007.