Mary’s birthday goes hand in hand with the Doctrine of Mary being “Full of Grace” or “Favored One” (Luke 1:28) Greater minds than mine have taught and explained this doctrine so I present you with the following examples.
Here is what the Catechism of the Catholic Church (CCC) has to say:
“Even before the terms “original sin” and “immaculate conception” had been defined, early passages imply the doctrines. Many works mention that Mary gave birth to Jesus without pain. But pain in childbearing is part of the penalty of original sin (Gen. 3:16). Thus, Mary could not have been under that penalty. By God’s grace, she was immaculate in anticipation of her Son’s redemptive death on the cross. The Church therefore describes Mary as “the most excellent fruit of redemption”” (CCC 508)
Click here to read what the very first Christians had to say on the matter.