The causes of phlegm in the throat of newborns are generally caused by laryngeal cartilage dysplasia or colds, as follows: 1, laryngeal cartilage dysplasia: consider the baby’s laryngeal cartilage dysplasia, caused by laryngeal tissues collapsing into the larynx during inhalation, resulting in the laryngeal lumen becoming smaller and the airflow through the obstructed airway produces a high pitch, vibratory wheezing sound, which sounds like phlegm in the throat. If it does not affect the baby’s normal breathing and breastfeeding, it usually does not need treatment, and can be observed at home, and can be self-cured at the age of 1-2 years. 2, caused by colds: Consider the symptoms of phlegm in the throat because of colds, because the baby will not cough up the phlegm, phlegm will be with the breath in the airways up and down the sound, often accompanied by fever, sneezing, runny nose, coughing and other symptoms. Parents are advised to consult their pediatrician and give anti-flu and phlegm medication to improve the symptoms of phlegm in the baby’s throat.