It is possible to become pregnant two months after missing a Depo-Provera birth control shot, according to the Center for Young Women's Heath at Boston Children's Hospital. Depo-Provera is a female hormonal method of birth control that is more than 99 percent effective.
Each Depo-Provera injection provides three months of protection against pregnancy. It is safe to get an injection up to 2 weeks early. Even though the progesterone in the Depo-Provera shot provides protection against pregnancy for more than three months, or 13 weeks, another type of contraception should be used if the injections are stopped altogether or an appointment is missed, according to the Center for Young Women's Health. Depo-Provera injections do not protect against sexually transmitted diseases and infections.