The symptoms of coughing with phlegm in the throat of a three-month-old baby can be seen in the following cases: 1. Acute cold, there will be runny nose, congestion, cough, phlegm in the throat, or systemic symptoms of fever, irritability, lack of love for milk, etc. 2. Acute pharyngitis can also lead to irritating cough with phlegm in the throat, sore throat, fever and other symptoms. 3. Parents should pay enough attention to the risk of laryngeal edema, upper airway obstruction, and asphyxiation, so they must go to the hospital in time for the doctor to diagnose the problem and use intravenous antimicrobial and hormonal drugs and nebulized inhalation therapy according to the severity of the disease.