It only lasted two days and was a really small amount of blood, not even enough to fill a panty liner. It was dark brown in colour, so old blood I guess. It was right around when my period would normally have been due and after the couple of days of spotting I kept expecting it to start properly, but it never did! I always had quite light periods anyway but this was noticeably lighter, and a different colour to normal.
I believe some women can have this sort of bleeding for the first few months of pregnancy but mine was only that very first month. I took a pregnancy test 1 week after my period was due and it came up positive so the bleeding obviously didn't affect the results of the test.
I saw your other post and hope things work out well for you. I'd been off the contraceptive pill for 5 months when I got pregnant and I still didnt know whether my body was coming or going. I had had cycles ranging from 26 days to 52 days and my premenstrual symptoms seemed to be different each month. If you're like me then it's just so hard to tell if your body is doing something different because it changes every month anyway. The only way to know for sure seems to be to take a test.