The cause of spitting in the mouth of newborns may be related to factors such as expelling amniotic fluid from the mouth and pediatric pneumonia. 1. Discharge of amniotic fluid in the mouth: During birth, the newborn is squeezed by contractions and the birth canal, which may squeeze in a small amount of amniotic fluid in the mouth. After birth, the newborn establishes independent breathing, but the swallowing function is not yet perfect, so it can only discharge the amniotic fluid in the mouth by spitting. 2. Pediatric Pneumonia: When a newborn baby suffers from pneumonia, the symptom of spitting will appear. Because the neonatal nervous system is not yet well developed, the cough reflex is poor, when the neonate breathes, the phlegm in the trachea is discharged out of the mouth with the neonate’s breath. It is accompanied by symptoms such as drowsiness, poor mental status, poor appetite, and red or blue color. Newborns spitting foam in the mouth may be caused by other reasons, should consult a doctor in time to identify the cause of the disease to give symptomatic treatment to improve the symptoms, so as to avoid delaying the condition.