However, the United States Food and Drug Administration only approved its use about 10 years ago. Depo-Provera is a hormonal, injectable contraceptive given every 12 weeks. Estrogen is associated with more serious health risks than progesterone. Progesterone-only methods are safe for use in women who, for medical reasons, cannot take estrogen. If a woman keeps her injection appointments, as scheduled, every 12 weeks, the risk of pregnancy is 0.
Progesterone also causes thickening of cervical mucous.
This effect impedes the progress of sperm through the cervical canal. However, after discontinuance of this method, it may take several months for your periods to become regular once again. The noncontraceptive benefits of Depo-Provera use are similar to oral contraceptives and include decreased bleeding or no bleeding, decreased menstrual cramps, and no ovulatory pain. The primary side effect of Depo-Provera is irregular bleeding. This tends to occur in the first year of use.