The
Depo is one of the most effective birth controls on the market, but has some
side effects that put women off. (I'd never personally use it. I went with a non-hormonal IUD) Side effects you might get are odd spotting, heavy/lighter than normal periods and over time no period, weight gain (this is a real common one) headaches, breast tenderness and a few other I can't think of. You can google for a proper list of side effects and the number of women who experience them.