I wouldn't stress too much (easier said than done) . If they find it to be a non-innocent sounding murmur, they will do an echocardiogram to find specifically what is causing it. We went through this 2 days after birth to find our daughter has a ventricular spetal defect. This is a small hole in the wall b/t two chambers of the heart. We are also meeting with a ped cadiologist early next month but were told since the size of the hole is small, they ususally close on their own.
It is so scary to hear any unsettling news about your babies heart but a majority of the time we worry for naught. If you want, do a search on congenital heart defects (CHD) online. They are more common than people realize (1 in 100 babies).
My first reaction when hearing this was, "what did I do during pregnancy to cause this" I founf the answer was 'nothing' CHD usually happen within the first months of life when the heart is forming and is just something that randomly happens. If you have any other questions, feel free to PM me - we are quicly becoming experts in this field