A woman may conceive as soon as three to four months after her last Depo-Provera shot, but conception may take as long as a year or two, according to WebMD. The length of time that a woman received Depo-Provera injections does not seem to impact this time frame.
Reproductive endocrinologist Christopher Williams, M.D., writing on Parents, notes that it takes some time for the body to adjust once a woman stops taking any type of hormonal birth control, including Depo-Provera. Ovulation may not occur right away. Dr. Williams recommends stopping Depo-Provera injections nine months before a woman wishes to conceive, but he warns that once a woman stops using birth control, conception can occur at any time.