Sounds like having a baby in the last year of your work is a good idea.
Most women I've known have done that and haven't had any problems. The
work is almost done, lots of writing up of the thesis and papers which is
all pretty convenient. The other advantage is that you can take off
between grad school and your post-doc, assuming that's ok financially, and
you get to start your post-doc off full blast (assuming you've now
adjusted to three hours of sleep per night). It does seem like a lot to
handle, but everyone I know is very happy.