I've never heard of anyone avoiding UC patients taking 6mp on UC dosages. Under chemotherapy for a cancer patient, they are typically on multiple strong dosed immunosuppressant medications simultaneously, making their immune system much, much weaker in order to fight cancer, therefore a nurse might want to avoid accidently giving them a cold, flu, or other ailment that they might, themselves, be carrying. Again, UC dosages are much lower than used for many other ailments, so that must be taken into account when considering it's use with UC as the total immune suppression is a lot lower. For UC, I'd say take extra precautions when you know someone around you is sick (frequent hand washing, keep a distance if they're coughing, etc.). I was never sick any more than normal while on 6mp, but I was a lot more careful during cold and flu season.
There are a number of moms who had happy and healthy babies while they were on 6MP. It's important for the mom herself to be in the best health during the pregnancy for her and the baby's benefit to ensure the best outcome, and that often means using medications like 6mp. I believe the vaccination schedule is changed/delivered after delivery.
Here's some good information on the various UC medications and their use during pregnancy from our resources section.
From conception to delivery: Managing the pregnant inflammatory bowel disease patient
www.ncbi.nlm.nih.gov/pmc/articles/PMC3974516/The Second European Evidenced-Based Consensus on Reproduction and Pregnancy in Inflammatory Bowel Disease
ecco-jcc.oxfordjournals.org/content/eccojc/9/2/107.full.pdfGood luck!