Mary is the new Eve, she is the Ark of the Covenant. Do you really think that God, The Almighty, the Holy of Holies, the Great I Am, would allow Himself to be born of a sinful woman? Do you not see the folly in this type of thinking?
Even His commandments were placed in a golden ark made to the Lord’s specifications. The Son of God could only be conceived in someone pure and sinless.
So then I can argue how was Mary born sinless inside a sinful body? I always saw it as Jesus was man, but not of Mary or Joseph. He was created as Adam was pure and sinless, but unlike Adam he was also God.