The blue triangle of newborns is mostly seen in hypoxia, congenital heart disease, pneumonia and so on. 1. Hypoxia: It may be caused by hypoxia in the perinatal period or by crying, which will easily lead to symptoms such as blue triangle and blue lips, and severe hypoxia may also lead to weak respiration. 2. Congenital heart disease: If the newborn suffers from congenital heart disease, it will affect the blood supply of the heart, and may also lead to other discomfort symptoms, such as blue triangle, shortness of breath and other symptoms. 3. Pneumonia: Bacterial, viral or mycoplasma pneumonia may be caused by improper care, resulting in symptoms such as coughing, sputum, and a blue triangle. There may be other reasons, such as physiological factors, for the newborn’s blue triangle. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.