When can implantation bleeding occur?

Implantation bleeding can occur anytime from 6 to 12 days after conception, but it usually occurs around 10-11 days. It is thought to be caused by the small blood vessels in the lining of the uterus breaking when the fertilized egg implants into the uterine wall. Implantation bleeding is usually light spotting or bleeding that lasts for a few hours or days. It is not as heavy as a normal menstrual period, but can still be a sign that implantation has occurred.