This medication is a combination of 2 hormones (an estrogen and a progestin) and is used to prevent pregnancy. It works mainly by preventing the release of an egg (ovulation) during your menstrual cycle. It also can work by making vaginal fluid thicker to help prevent sperm from reaching an egg (fertilization) and by changing the lining of the uterus (womb) to prevent attachment of a fertilized egg. If a fertilized egg does not attach to the uterus, it passes out of the body. There is a small amount of iron (ferrous fumarate) in each of the 4 inactive tablets taken during the fourth week. (The inactive pills do not contain any hormones). These tablets are meant to keep you in the habit of taking 1 tablet each day and do not have enough iron to treat iron deficiency.Besides preventing pregnancy, birth control pills have been shown to help make your periods more regular, decrease blood loss and painful periods (dysmenorrhea), and decrease ovarian cysts.Use of this medication does not protect you or your partner against sexually transmitted diseases (e.g., HIV, gonorrhea, chlamydia).