First, I'm sorry to hear of your miscarriage.
I don't know of any hard data or studies that show whether or not laser treatment for PWS could affect pregnancy. When you have your appointment, make sure that you make the doctor understand that you will be trying to get pregnant next year. He may have a better alternative or literature to help you make a decision like that.
Have you considered waiting until after your pregnancy and getting the laser treatments done then? I know it seems a long time to wait, but maybe they could take care of the stretch marks (yes, there will TOO be stretch marks
) at the same time.
I'll look around and see if I can find any information on that, though.