Hello Sir........my Son Is 2 Months Old Baby And He

hello sir........my son is 2 months old baby and he has ASD of 6mm .....doctor said it is not dangerous as much ....it will be closed after 2 or 3 year automatically.....is it possible sir....because his weight is also not good he is only 3 kg.....but every time we check at our child specialist he is improving his weight with gaining part......but still i am so worry about his....i read lots of articals Of ASD ......plz guide me sir