Many babies make odd noises during the night – some babies grunt and groan in their sleep, you may hear gurgling tummies and other digestive noises, and some babies coo, sigh, or whimper. While it might be unexpected to hear your baby’s sleep noises, they are certainly common as babies spend a lot of their sleep time in active sleep where they are processing information and probably dreaming. While there is research on the effect of noise on infant sleep, we have been unable to find any research into the sleep noises made by babies themselves. Most information we could find was anecdotal.
Swallowing gurgling noises are most likely related to babies having an immature swallow reflex and a tendency to regurgitate a little milk every now and then. They can make loud breathing sounds because, to begin with, babies are predominantly nose-breathers so they can suck and breathe at the same time. Sometimes babies cough on their own saliva or mucous. Sleep sounds resolve gradually as the baby matures and spends less and less time in active sleep.
If your baby has persistent sleep noises that you are worried about it is best to seek medical advice.