In the pregnancy forum (edited because i just realized i'm in the pregnancy forum lol), you'll find a few posts dealing with the topic of having another child--the physical ramifications and the stresses it can put on your body, family and lifestyle. Also, the hows of handling treatments and baby schedules.
I think a lot depends on your health stability and whether your spouse or someone else is available to handle both kids while you are tied up with nebs and such. Also whether you have family and other kinds of help nearby. I've a ten-year-old (and 9 and 7) and it just occurred to me as I thought on this subject that if I had a new baby, there'd be temptation to use the oldest as a built-in babysitter, which is something you'd want to think about carefully/not assume/not overdo.