What Causes Pink Spotings With Late Periods?

I had my tubes clipped last march after a 18 week fetal demise. My periods have been regular ever since (28 - 30 days) my period this month is a week late but I have had a very light pink spotting that is only visiable every now and then when I wipe. This has been going on for the last two days. Do u have any idea what could be going on?