This combination hormone medication is used to prevent pregnancy. It contains 2 hormones: a progestin and 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. 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).