When does implantation bleeding start after intercourse?

Near expected period: Implantation happens about 6 days after conception. In one study about 9% of women have 1 day of bleeding in the first 8 weeks of pregnancy. Just to be confusing, this tends to happen around the time you would have had a period. Some call this implantation bleeding. Remember, though, it is not very common. Only 9% or so. Best wishes!