Depo Provera (the shot) becomes effective 24 hours after your first injection and remains effective as long as you continue to get your shots on time. The main way it works is by preventing ovulation. Ovulation is the monthly release of an egg from the ovaries. When there is no egg available for the sperm to fertilize, you cannot become pregnant. Therefore, a male can ejaculate inside of the vagina, and you will still not become pregnant because there is no egg.
The shot does not protect you against sexually transmitted infections (STIs) though. To reduce your risk of STIs, you should use condoms in addition to Depo.
8. February 2012
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