Normal newborns can sometimes show cyanosis within 5 minutes after birth, because the arterial duct and foramen ovale have not yet closed, still maintain the right-to-left shunt, the lung has not yet fully expanded, the pulmonary ventilation function is not perfect and the peripheral skin is poorly perfused. 5 minutes later, the changes in the circulatory system have completed the complete separation of arterial and venous blood flow, the lips and nail bed become pink, but sometimes the skin is still mildly cyanotic, especially after birth exposure. In the cold environment, the local blood flow in the distal extremity slows down and reduces hemoglobin, so although PaO2 is not low, the extremity still shows obvious cyanosis, called peripheral cyanosis, and the cyanosis can be reduced or disappeared after strengthening insulation. 1, lung lesions: such as neonatal asphyxia respiratory congenital malformations, such as Pierre-Robin syndrome postnasal obstruction pulmonary hyaline membrane disease pulmonary expansion insufficiency, pneumonia pneumonia, swelling gas, chest congenital diaphragmatic hernia, congenital pulmonary arteriovenous, fistula sustained fetal circulation and other causes. Suggestions: in this case is often generalized cyanosis and accompanied by respiratory distress, win immediate oxygen therapy, it is best to send immediately to the doctor, so as not to delay the disease. 2, nasal blockage: newborns have mucus in the nasal cavity or boundary demented cause obstruction, but a mouth cry, cyanosis will disappear. Suggestion: During daily care, you can give your baby a cotton swab with water to wet the nostrils, soften the boogers and then slowly stick them out. Note that the action must be gentle, so as not to hurt the baby. 3, congenital heart disease: newborns have congenital heart disease, such as complete transposition of the great vessels, left heart dysplasia, tetralogy of Fallot, pulmonary valve and aortic valve stenosis, atrioventricular septal defect, etc. Due to cardiac malformation, some of the venous blood enters the arterial blood and causes cyanosis. Note: The diagnosis of congenital heart disease is clearly established when cyanosis is accompanied by a heart murmur, enlarged heart borders or heart failure. However, cyanosis can sometimes be present alone, and some very severe cyanotic congenital heart disease does not present with murmurs in the neonatal period, such as complete transposition of the great vessels and pulmonary valve atresia without the combination of other cardiac malformations, both of which have inaudible murmurs or no loud murmurs.