Implantation spotting is a slight bleeding or spotting that can occur when the embryo has implanted itself in the uterus. Implantation spotting is light red or brown, and usually takes place seven to ten days after ovulation, or about a week before the date of expected menstruation. If spotting occurs only a few days before the date of menstruation, then it's probably the beginning of menstruation and not implantation bleeding. Implantation spotting occurs in 20 to 30% of pregnant women.