This combination hormone medication is used to prevent pregnancy. It contains 2 hormones: norethindrone (a progestin) and ethinyl estradiol (an estrogen). It works mainly by preventing the release of an egg (ovulation) during your menstrual cycle. It also makes vaginal fluid thicker to help prevent sperm from reaching an egg (fertilization) and changes 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 pills taken during the fourth week. The inactive pills do not contain any hormones. These pills are meant to keep you in the habit of taking 1 pill each day and do not have enough iron to treat iron deficiency. Besides preventing pregnancy, birth control pills may make your periods more regular, decrease blood loss and painful periods, decrease your risk of ovarian cysts, and also treat acne. Using this medication does not protect you or your partner against sexually transmitted diseases (such as HIV, gonorrhea, chlamydia).