Hiring manager here also. As another poster upthread said, we often get 10 candidates who are equally qualified and can do the job equally well. My job as a manager is to make sure the work gets done with as little disruption as possible. We have an extensive, 1 year long training process. To have someone live in the middle of that is very disruptive. I get that some things can't be controlled but if know up front there might be issues, for whatever reason, I won't pick that person if I have nine other equally qualified candidates.
That said, if I have 10 fabulous candidates and during the interviews, the pregnant candidate is above the rest, impresses me, and looks like a good fit, I'd hire here and deal with the disruption for the long term gain. If she is NOT head and shoulders above, but equal, then I may not. Maternity leaves are tough to work around in my business. Very hard on the other team members because we cannot temporarily fill.