I am so sorry for your loss. My first pregnancy resulted in a miscarriage also, but that was before cancer. Miscarriage happens more often that most of us know, and as sad and painful as the experience was for you, it probably was not due to the chemo (assuming your regimen was ABVD). I have known a few women who have gone through ABVD and gone on to have beautiful, healthy babies after treatment with ABVD, and it is very uncommon that this regimen causes problems with fertility. The fact that you did manage to become pregnant is a great sign. I went on to have two beautiful daughters after my miscarriage.
Good luck and baby dust to you!