I've wondered this myself many times. For now, my MTX keeps me from getting pregnant until at least August 2015. I will be almost 36 yrs old. I'll be considered high risk in normal health, let alone someone who has Wegener's and Hashimoto's and isn't quite at 5 years remission from cancer.
Adoption has always been something we've considered and something we could do prior to coming off MTX. However, some other things come into play.
I was 17 when my mother died from raging pneumonia, and I was 20 when my father died from Alpha-1 antitrypsin deficiency and metastasized lung cancer. Being young and losing my parents devastated me. I had younger brothers who were under 10 when they died. It opened my eyes to a lot of things.
I don't want my children to be put in that position. I've carried that around with me wherever I go. Just recently, in the ER being prepped for emergency surgery for appendicitis, my stepmom came in and I joked that I was upset to have inherited my father's predisposition for being in the ER all the time. She laughed, but it felt true. Weird diseases apparently run in my family.
Genetically, I don't want to run the risk of passing my cancer riddled- weird disease germs onto children ... but, I could adopt and give a lonely child a warm loving family ... until I died.
I don't know. I'm a worrier.
I have seen lots of posts about people who've had children post diagnosis. It can be done!!!

Keep your head up! It can happen.