how old is your baby?when my baby was born until the age of 3 months there was also phlegm but my pediatrician said that until the age of 6 months it was natural that there was mucus in the baby's airway as long as it didn't interfere with breathing and didn't show symptoms of flu / cough / shortness of breath / fever. So until my child is 6 months old I just observe. fyi my child is now 11 months old.