The doctrine of the Immaculate Conception does not refer to the moment when Our Lady conceived Our Blessed Lord, but to the moment in which she herself was conceived by her mother, St. Anne. Nor does it suggest that Mary’s coming into being was physically in any way an exception to the ordinary laws of nature. What it does tell us is this: that even at that first moment of her conception, by which is meant the very first instant of Our Lady’s existence as a human individual, she was (by God’s favour granted in anticipation of the merits of her Son) preserved from all stain of Original sin.