The introduction to the lectionary, when speaking of the Sundays of Advent, says, "Each gospel reading has a specific theme: the Lord's coming in glory at the end of time (first Sunday), John the Baptist (second and third Sundays), and the events which immediately prepared for the Lord's birth (fourth Sunday)" (No.11).
We focus, in other words, on the first and second comings of the same Christ, and on the one who teaches us how to prepare for His arrival, namely, by repentance. "Reform your lives! The reign of God is at hand." The New Testament readings throughout Advent complement and expand on John the Baptist's exhortations of repentance.
The preparation for Christ's coming is reform, and the promise of His coming is reconciliation. The two, furthermore, are linked. If the Messiah comes to restore harmony between nations and people, then the people of the Messiah are to repent of whatever destroys that harmony. If the Messiah comes to bring justice ("He shall judge the poor with justice and decide aright for the land's afflicted"), then the people of the Messiah are to work to eliminate injustice. The "justice" referred to in Isaiah ll is an act of intervention to save the helpless.
Abortion is an injustice against the most helpless, and attacks the harmony of human relationships at their most fundamental and sensitive point, the relationship of mother and child. Preparing for the Lord's coming therefore requires a total rejection of abortion. The promise of His coming heralds a new harmony between mother and child.
The focus on the Virgin and Child at the end of Advent highlights this.
The Second Vatican Council reflects upon the relationship between the coming of Christ and our activity to prepare for it. In the Constitution on the Church in the Modern World, we read, "Far from diminishing our concern to develop this earth, the expectancy of a new earth should spur us on, for it is here that the body of a new human family grows, foreshadowing in some way the age which is to come....When we have spread on earth the fruits of our nature and our enterprise
-- human dignity, brotherly communion and freedom -- according to the command of the Lord and in his Spirit, we will find them once again, cleansed this time from the stain of sin, illuminated and transfigured, when Christ presents to his Father an eternal and universal kingdom...." (#39). In other words, the spirit of Advent should naturally bolster our pro-life efforts, and the progress we make in promoting human dignity becomes the "building blocks" for the eternal kingdom.
Advent leads the Church to the Silent Night when God Himself is revealed as one of us. This season leads us to the joy of His birth. May that birth shed protection on all about to be born, and as we work to end abortion, may we "wait in joyful hope for the coming of Our Savior, Jesus Christ."