Dark colored Discharge at 25 weeks?

S
Hey all,
Looking for you're experience and advice. Today I briefly had a darker bout of discharge. It appeared to have old blood - similar to the brown color of "implantation" bleeding. It was only once when I went to the bathroom, but it had me concerned. I called the doc and the nurse dos not seem concerned, as there was no accompanying  pain or cramping at all. 
Have any of you been through this this late in your pregnant?