MPA can be used for birth control in the form of an injection, and for this use if sold under the brand names Depo-Provera and DeposubQ-Provera 104. It works by altering the hormone imbalance during the menstrual cycle; the role of progesterone in the menstrual cycle is to prepare the uterus lining for implantation of a fertilized egg, and a drop in progesterone levels signals ovulation (the release of an egg from the ovaries). Injecting MPA interferes with this process, keeping progesterone levels high and preventing ovulation. Progesterone supplements such as MPA also have a thickening effect on the mucus in the cervix, which prevents sperm reaching the uterus in the event that an egg is released.