Implantation bleeding is a pink or brown vaginal discharge which some women may observe 3-7 days after embryo transfer. This discharge occurs when the embryo implants in the uterus, which is why it is referred to as implantation bleeding. As the embryo grows, it invades into the uterine lining, in order to establish a blood supply and get nutrients from the maternal circulation. Sometimes this invasion of the mother's blood vessels will result in leakage of blood and result in implantation bleeding.
Please do remember that most women do not experience implantation bleeding, because this tiny amount of blood often gets reabsorbed silently, so you do not need to worry if you do not have this spotting.
Many women get scared when they see the implantation bleeding . They assume that this means their period is about to start and that their embryos have failed to implant . It's true that it's very difficult to differentiate between the start of the period ( premenstrual spotting ) and implantation bleeding.
Often the implantation bleed is simply a bit of brown or pink colored discharge mixed in with a clear discharge. Cramping, backache, or increased bleeding does not usually accompany implantation bleeding.
If you do have implantation bleeding, please do not panic. Ignore it; continue all your luteal phase support medications; and do the HCG pregnancy blood test as planned.