Can an egg implant during menstrual bleeding?

It is possible for an egg to implant during menstrual bleeding, although it is not common. Menstrual bleeding usually occurs when the lining of the uterus (the endometrium) sheds after an egg has not been fertilized. However, in some cases, an egg can be released from the ovary and fertilized just before or during menstrual bleeding. If this happens, the fertilized egg can implant in the endometrium and begin to develop. This is known as implantation bleeding, and it can be mistaken for a menstrual period. Implantation bleeding is usually lighter than menstrual bleeding and may only last for a few days. If you are concerned that you may be pregnant, it is important to take a pregnancy test.