1. in God’s presence, sin cannot stay, it is destroyed.
2. Jesus in the womb was still Jesus Christ, Lord and God.
3. To protect the bearer of God, she had to be made filled with grace and she had to be made free of sin — for her to be able to bear the Lord
now her own parents being sinful did not affect this as mary is just a creature, and sinlessness being in contact with sinfulness does not affect sinlessness (e.g. a newborn baby in contact with a sinful mother), but the blazing power of God that destroys anything that is tainted with sin, if that is kept in a box/womb which has even a slight tain of sin, that box/womb will be destroyed.
~ by Cronos