Implantation happens when the fertilized egg, the blastocyst, has completed its travel through the fallopian tube and attaches to the lining of the uterus. The blastocyst is a cluster of tiny cells, smaller than the head of a pin.
Implantation and implantation bleeding occur on average about 9 days after ovulation (range between 6-12 days), which is about a week to a few days before your period would normally start.
Spotting that occurs around a week after ovulation can be implantation bleeding; whereas spotting that occurs much later and a couple days before your period would normally start may not be. A normal menstrual cycle generally starts off light and then gets heavier.
What you may consider to be implantation spotting can sometimes be the sign of an early period and that means you are not pregnant. If this is the case, the spotting will pick up to heavier bleeding. If you have spotting right around the time your period would normally start, it can be more confusing. You will need to take the wait and see approach or take a pregnancy test to determine pregnancy.
Some women report having around that time implantation symptoms like implantation cramps, implantation bleeding or implantation cramping.
Implantation bleeding usually consists of a couple of drops of blood, which can be either red or brown. If the bleeding is heavier more like a period, then it's unlikely implantation bleeding.
Most pregnant women, however typically have little to no symptoms on the day of implantation and do not experience typical implantation bleeding, while some women who are not pregnant may experience some spotting which they believe could be implantation.