Heart murmur in 3 month old.. what should I expect?

I had Aubree at the doctors last week she has been going every 2 weeks so that doctor can monitor her acid reflux and her weight... but anyway the doctor said that she heard a loud heart mumur.. and wants us to go see the cardiologist.. my question is Aubree has never had a heart murmur before... shes three months old.. shouldn't they have found this before... They listen to her lungs every doctor visit... and do you think I should worry over this?

[hanacabana]

I know this probably doesnt help but ive been told that heart murmurs in babies are extremely common. Its something to do with the way their heart closes up during birth/the first breath (from being a foetus to a baby and getting oxygen from air rather than the placenta). Because their heart beat is so much faster than ours its often hard to hear them. In almost all cases this clears up. Im sure its nothing to worry about and the doctor just has to be sure for legal reasons. It definitely doesnt sound worth worrying about until you have spoken to a professional. Goodluck with you appointment :)