Implantation bleeding

Implantation bleeding

Bleeding and spotting are common during the luteal phase of the menstrual cycle, and early stages of pregnancy, but are unrelated to implantation. Implantation bleeding occurs between 7 and 14 days after fertilization, and is a small amount of light vaginal bleeding or spotting that can occur in early pregnancy due to the blastocyst penetrating the lining of the uterus during implantation. By day 13 the penetration site in the endometrium has usually been closed by a fibrin plug but increased blood flow into the syncytiotrophoblast spaces can sometimes cause bleeding at that site. Implantation bleeding may be accompanied by symptoms such as cramping, nausea, breast tenderness, and headaches. Implantation bleeding can be distinguished from period bleeding by color, clotting, strength and duration of flow.