I used the vest, pulmozyme, and an albeterol inhaler during my entire pregnancy. When I got really fat, I still used it but just snapped the top buckle. I also had my husband do some PT at that point. I also continued taking my enzymes and certain antibiotics through the pregnancy.
I wasn't on TOBI at the time, but started doing it after I had my baby and was breastfeeding. I also have a friend who was on TOBI trhoughout her pregnancy- her OB and CF doctor told her it would be fine. There seems to be some contraversy about whether or not TOBI is safe during pregnancy (or breastfeeding) but after asking a lot of questions at clinic at doing quite a bit of research on my own, I decided to continue breastfeeding on TOBI. I know it's kind of a different situation, but either way I think you have to research it, weigh the pros and cons, then make your decision.