Congratulations, Mike! And to your wife as well.
One of our members at the dojo trained into her eighth month even taking ukemi. She asked people to punch her in the chest rather than stomach for tsuki, though. Otherwise, she worked a little bit more slowly than before but pretty consistently.
I seem to remember hearing that Pat Hendricks sensei was teaching up to the day (or the day before) her delivery.
I think, though, that this sort of thing depends from person to person. I think it's best your wife talks to her doctor about this sort of thing as her circumstance might be different than those of other people here.