回複：Can I submit medical examination to the Service Center?

If you submit it now, they can put it in your I-485 folder. Once they decide to process your case, they have a complete application (given that you have provided all the other forms and evidence). Otherwise, if you wait until they ask you to do so, your case will definitely be delayed. In case they lose your medical examination, you can ask your doctor to fill another form for you. Anyway, this is only a suggestion.