I am 6 days post op tummy tuck and I have a cough with phlegm. Is this going to damage my results?

Coughing will not ruin your results after having a tummy tuck. Make sure to stay in your abdominal binder at all times to protect the muscle plication that was performed during your operation. I would also recommend hugging a pillow against your tummy when you have to cough. This will also help to support theabdomen.  

 Early out of tummy tuck surgery, the concern with your description would be, the potential for disruption of sutures that are holding the abdominal wall muscles together in the midline.  

In general, it would take a significant amount of pressure to “tear" the muscle repair after tummy tuck surgery. This event would likely be associated with significant discomfort. A change in your physical examination, such as increased swelling, bleeding, a new onset "bulge" would also be likely.

Generally speaking, abdominal wall muscle plication performed during tummy tuck surgery is quite secure; disruption is very unusual. You will be best off following up with your plastic surgeon who will be your best resource when it comes to accurate assessment, advice, and/or meaningful reassurance.

Best wishes.