M.A.
Hi,
Both of my children were diagnosed with heart murmurs before they were 6 months old. I have no idea what "grade" theirs were. What it meant for us is that we had to put them on antibiotics before every dental appt. and tell any specialist about it. (Surgeons, etc.) After worrying about this for a couple of years, we finally had our oldest go through a very intense cardiac workup, which found that her murmur was benign. (Of course, that's when we were covered under a really good HMO quite a few years ago....) We don't have to give antibiotics anymore, and the workup was invaluable when my daughter had surgery to remove her tonsils and adenoids last year. (I was told that the anesthesiologist could refuse to do surgery if he was concerned in any way about it. the report took away that risk.)
Definitely follow up with your pediatrician, because the murmur might not be innocent or benign; However, it could be. Good luck!