Currently, critical congenital heart disease is not detected in some newborns until after their hospital discharge, but some may be detected by routine pulse oximetry performed on asymptomatic newborns after 24 hours of life. The American Academy of Pediatrics has published a statement on the topic.
Role of Pulse Oximetry in Examining Newborns for Congenital Heart Disease: A Scientific Statement from the AHA and AAP (Full Text)