For anyone who may stumble upon this thread, as I just now have in looking up this question, the best answer is here:
catholicforum.com/forums/showthread.php?11870-Did-the-Virgin-Mary-suffer-the-pains-of-childbirth
Please read the whole thread, as it is a solid answer to this great question!
This is a very important issue in Church Teaching. Just as the conception of Jesus was mystical and bound in purity, so was His birth.
The Virgin Mary did not suffer pain in childbirth.
From the Catechism of the Council of Trent:
But as the Conception itself transcends the order of nature, so the birth of our Lord presents to our contemplation nothing but what is divine.
Besides, what is admirable beyond the power of thoughts or words to express, He is born of His Mother without any diminution of her maternal virginity, just as He afterwards went forth from the sepulchre while it was closed and sealed, and entered the room in which His disciples were assembled, the doors being shut; or not to depart from every-day examples, just as the rays of the sun penetrate without breaking or injuring in the least the solid substance of glass, so after a like but more exalted manner did Jesus Christ come forth from His mother’s womb without injury to her maternal virginity. … To Eve it was said: In sorrow shalt thou bring forth children. Mary was exempt from this law, for preserving her virginal integrity inviolate she brought forth Jesus the Son of God without experiencing, as we have already said, any sense of pain.
CATECHISM OF THE COUNCIL OF TRENT
PART 1: THE CREED
Article III
We can also know what the Church believes from her prayers:
In the preface of the votive Mass in honor of Mary at the foot of the cross, we read the words: “She who had given Him birth without the pains of childbirth was to endure the greatest of pains in bringing forth to new life the family of the Church.”
cst-phl.com/marian.html
On the contrary, Augustine says (Sermone de Nativitate supposititious), addressing himself to the Virgin-Mother: “In conceiving thou wast all pure, in giving birth thou wast without pain.”
I answer that, The pains of childbirth are caused by the infant opening the passage from the womb. Now it has been said above (Q28,A2, Replies to Objections), that Christ came forth from the closed womb of His Mother, and, consequently, without opening the passage. Consequently there was no pain in that birth, as neither was there any corruption; on the contrary, there was much joy therein for that God-Man “was born into the world,” according to Isaiah 35:1,2: “Like the lily, it shall bud forth and blossom, and shall rejoice with joy and praise.”
SUMMA THEOLOGICA
Q35,A6