Ooh. I just found this, so thought I'd share:
"What is implantation bleeding?
Implantation bleeding can occur when the fertilized egg burrows into the lining of the uterus. This process is known as implantation. Every newly conceived baby must implant, however, not every implantation will cause noticeable bleeding.
When does it happen?
A fertilized egg implants anywhere from six to ten days after fertilization. For example, if you ovulated on day 14 and conceived on day 15, you could experience spotting any time from day 21 to day 25. If you ovulate later in your cycle, implantation bleeding may also occur later. In some cases, women experience spotting on the very day they are supposed to start their period. For this reason, many women who are pregnant confuse this spotting with a true period.
How common is it?
About a third of women who become pregnant will experience light spotting, or bleeding during implantation. You may experience implantation bleeding with every pregnancy, or with none of your pregnancies.
How can I tell the difference between implantation bleeding and a real period?
Timing: Bleeding that is caused by implantation generally occurs a few days before the woman should start her period. In other cases, the bleeding may not begin until the woman should have started her menstrual cycle.
Appearance: Implantation bleeding is generally very light pink or brown in color. Occasionally, there may be a few brighter red specks, but for the most part, this bleeding looks like "old" or "faded" blood. Clots are not usually passed during implantation bleeding.
Flow: Implantation bleeding is generally quite scant. Most women use only a panty liner for several hours and find that it is more than adequate to meet their needs.
Duration: Implantation bleeding lasts from 1 to 3 days. It may appear on day 1, 3 and even 5, but rarely extends beyond that."
Sorry if you weren't interested. Lol.
xx