I've worked in oncology for 8 years; had three children while working there. As previously said, you won't be handling chemo, but would need to use universal precautions when handling urine/stool/vomit etc. You need to avoid patients with active CMV virus; which the nursing staff at the hospital would be able to arranged. It's not a danger at all for you to be on the unit. Relax and go with whatever your instructors feel is best for you. Good luck and feel good!