Implantation bleeding typically occurs 6–12 days after ovulation, which is generally 3–12 days before a missed period would arrive. This timing places it in the window when a period might otherwise be expected, making it easy to confuse with menstrual bleeding.
Implantation bleeding happens when a fertilized egg attaches to the uterine lining. It is usually lighter and shorter than a normal period, lasting only a few hours to a couple of days. The bleeding is often described as minimal spotting rather than a heavy flow, and the color may be lighter (pink or brownish) compared to typical menstrual blood.
Since implantation can occur relatively late in the cycle, bleeding from implantation and the start of a period can overlap in timing. However, they are distinct events: implantation bleeding is caused by the embryo embedding itself, while a period occurs when the uterine lining sheds due to falling hormone levels after an unfertilized cycle.
If you experience unexpected light bleeding and suspect pregnancy, a blood test measuring hCG (human chorionic gonadotropin) can provide definitive confirmation even before a missed period. Home pregnancy tests are typically most reliable from the first day of a missed period onward, though some sensitive tests may detect pregnancy a few days earlier.