Atrial septal defect 2mm in newborns does not require treatment. Atrial septal defect of 2mm in newborns is a mild atrial septal defect, and usually, small atrial septal defects can be self-healed when the child is one and a half to two years old. It is recommended to check cardiac ultrasound once every six months to observe the condition of atrial septal defect. If the atrial septal defect is still present after two years of age, but has not increased significantly, and the child does not have symptoms caused by the atrial septal defect, such as chest tightness, panic attacks, and cyanosis during activities, the cardiac ultrasound can be repeated periodically. If the atrial septal defect is progressively increasing in size, greater than 5 mm, or if there is restriction of movement with chest tightness, panic and cyanosis, it is recommended to perform atrial septal defect occlusion or atrial septal defect repair.