A. Tachypnea that persists after 2 hours of life, with mild respiratory distress, according to the Silverman Anderson Bulletin, if possible.
B. Self-limited tachypnea worsening up to 24 to 48 hours and later improvement. Resolution frequently up to 72 hours, until the 5th day of life.
C. Newborns who have diagnosed extrapulmonary conditions that also have tachypnea: infection, cardiological, neurological, metabolic diseases will be excluded from the diagnosis.
D. Chest radiography showing diffuse interstitial infiltrate with distribution pattern from the hilum, thickening of the lobar fissure, or opacity by perihilar reinforcement. There may be mild to moderate cardiomegaly.