I'd think first. And then I would inform him/her that cancelling the show is the absolute last thing that can happen, since hopes are already up, tickets have been sold, and houses have been sold out. I'd make sure to communicate that at this point, the show has momentum; check lists are made, ops will be trained, the actors know what they're supposed to be doing and the musicians know what they're supposed to be playing. Continuing the show is not only possible, but relatively easy at this point.
Assuming I'm not a high school student(maybe I'm on the worst college internship ever), I'd consider that from Tech onward, the SM is ideally running the show, and would conceivably have the respect of the cast(it's a stretch, I know), and their cooperation. I'd try to remember/decide what the director would have wanted to do schedule-wise for Tech(if it wasn't already written down). I'd ask if there was an actual need to have a director present, and if so, I would offer to contact some local directors to observe and assist with Tech, since it's an emergency(I'm also assuming there's no AD).
I'd ask if we know how the director and the baby are, and then probably spend the time before rehearsal freaking out with my book. But at rehearsal, I'd gather the cast and crew, and tell them that the Director is squeezing out a baby, but this is the point where the show transfers to the SM, and they are in good hands.
Onward to tech!