My 4 month baby is coughing and her breathing sounds congested but no fever?

Other symptoms? Watch baby closely. If they are feeding well, interacting with mom in a normal fashion, remain without fever, and the cough is not producing anything which looks like pus, and they are not having obvious trouble breathing and their color remains normal you can ride this out. If, however, anything gets worse, if they are irritable and not feeding normally, short of air, etc., get them to doctor.