I get that Bajorian customs are for the women to be totally relaxed to help with the birthing process
It's not a custom, it's actually part of the biological process for Bajorans. The endorphins start pumping, and the woman has to relax to a certain point. When they get there, the baby just slides on out.
Exactly. It's not that they feel no pain - it's that the body creates enough endorphins to counteract the pain. The problem Kira faced in those scenes was that there were so many
endorphins in her system that it was reaching dangerous levels and she had to back off and let the endorphins reduce.
Frankly, it sounds like a better system than ours.