Birth Control Injections:
Birth Control Shots are a long-acting form of progesterone, a hormone that is naturally manufactured in a girl's ovaries. The shot is given as an injection in the upper arm or in the buttocks once every 3 months to protect a women from becoming pregnant. The hormone progesterone in the birth control shot primarily works by preventing ovulation (the release of an egg during the monthly cycle). If a women doesn't ovulate, she cannot get pregnant because there is no egg to be fertilized.
Depo Provera is a birth control shot that is given every three months. Women may have irregular bleeding, constant bleeding, or the lucky ladies who have no periods while on Depo Provera. If you have constant bleeding on Depo Provera, the best thing is to wait for the shot to completely leave your system. This may take 6 or more months to have regular periods after an injection is given. New recommendations: only use the Depo Provera injections for 2 years maximum.