[margaritaville]

Disclaimer: My knowledge base is humans not pets. It's possible that since this little one may have been from a second breeding, she may be a little premature. In humans it sometimes happens when they are premature that the valve between the oxygenated and non oxgenated blood in the heart has not yet closed thus hearing the murmur. Your vet is the best answer to the long term answer as to rather or not it can eventually close.