Catholic Corner
Question: What is the meaning of Immaculate Conception?
Answer: As is made clear in Pope Pius IX's official definition of the Immaculate Conception of Mary, only God's intervention made it possible for Mary to be conceived without original sin: "The most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved free from all stain of original sin" (December 8, 1854).
"Although as a descendant of Adam in a sinful human race Mary would naturally have incurred the guilt of original sin, a special divine decree kept her free from it in light of the foreseen or anticipated merits of Jesus Christ" (The Teaching of Christ, Our Sunday Visitor). Dr. Alan Schreck explains it this way, "Mary actually was the first to be saved by the grace of her Son, Jesus. God first applied to Mary the grace that he knew and foresaw that Jesus would gain by his life and death on the cross" (Basics of the Faith, Servant).
Thus, the fact that Mary was conceived without original sin had nothing to do with the sanctity of her parents or her own holiness, but everything to do with God's plan for the salvation of the world.
From Pastoral Answers To Questions About The Faith By Fr. John Patrick Bertolucci