I second Alan's welcome. And many partners post here.
There is good news and not quite so good news with your husband's diagnosis. 0is means that the bladder cancer has been found at the earliest possible point, and the "is" indicates that it is what is called "carcinoma in situ" or "CIS" which is high grade. As you may have read, BCG is the treatment of choice for CIS. Mitomycin is also sometimes used, particularly if the patient is unable to handle BCG for some reason or if, as has been happening recently, BCG is not available. BCG is a wonderful treatment to have available for CIS as it is often curative. I was diagnosed 11 years ago with CIS, underwent BCG induction treatments and then maintenance treatments and am (anxiously) awaiting my 11th year exam (and all clear?) in about two weeks. Your husband will, we trust, have the same result!
BCG is a live, if modified, TB bacterium that was developed almost 100 years ago as a vaccine for children. Of course some caution is always indicated with its use. Your husband, should his doctor prescribe it, will receive complete instructions about how to deal with it. He should discuss your pregnancy with his urologist and you should definitely discuss the situation with your OB. I suspect that part of their advice would be for him to use a separate bathroom, if possible, and take care of his own disinfection issues with you staying away from it. As Alan said, individual medical advice needs to come from your doctors since they are familiar with your situation and we are not doctors. Just be sure to make a list of all the questions you might have and be sure to ask them and get answers that you are satisfied with.
I am sure that he, and you, and your little one will do fine.
Sara Anne