This idea that Mary experienced NO pain seems a complete misreading of Genesis and a faulty application of doctrine.
Right: the idea of Mary’s painless birthing of Jesus doesn’t proceed from a reading of Genesis, but from a particular interpretation of the dogma of Mary’s perpetual virginity. Namely, this interpretation asserts that a virgin birth necessarily has physical implications, among them being a pain-free birth.
(Often, the explanation for this assertion points to the catechism of Trent, which makes precisely this claim. However, I think it’s valuable to point out that this is a
biological claim rather than a
theological one. And, if we look at that same catechism, in its description of Jesus’ conception, we see that it makes the biological claim that Jesus is conceived of Mary’s blood. (This is the same error of reproductive biology that Aquinas makes, and which leads
him to reject the Immaculate Conception.) So, I think I would ask this question: if the catechism of Trent, in explaining theological dogma, makes an error of biology (which does not affect the truth of the dogma) in explaining Jesus’
conception, is it unreasonable to suggest that their biological assertions on Jesus’ birth aren’t an infallible declaration of dogma? (I would answer ‘no, it’s not unreasonable’… and I’m sure that would send some into a tizzy…

) )