Re: Random punter question of the night
I don't claim to be an expert, but as my wife is currently 34 weeks pregnant with #2, I'll at least render a guess with some observations.
High frequencies would be attenuated most - I would guess there wouldn't be much above 1K that would make it through (ultrasound machines use "ultrasound" obviously, but the signal is around 150dB - a little different from the average PA signal), and low frequencies would be hardly attenuated at all. Our kid has jumped when I talk in the vicinity of him/her in a medium voice, so clearly the kid can hear that. Our church service's music runs usually in the mid '90's C-weighted and my wife has never noticed the kid being unusually active at that time.
When babies are newly in "outside mode", it is customary for parents to not have them in the service during music for hearing protection reasons.
Since I don't particularly enjoy spending time in places where the sustained levels are above 100dB, I don't take my family there either - pregnant or otherwise, which would be my personal answer to the question.
