Immaculate Mary, Matchless in Grace | John Saward | Two excerpts fromCradle of Redeeming Love: The Theology of the Christmas Mystery
First excerpt, from the Introduction:
Glorious above all the other Christmas companions of Christ is the Blessed Maiden who gave Him human birth. At the Matins of Christmas Day, the Church cries out: 'Blessed Mary, the Mother of God, whose womb abideth intact, hath this day given birth to the Saviour of the world." 
Each day of the octave, in the Canon of the Mass, the Latin Church venerates the 'inviolate virginity' that 'brought the Saviour into this world' and dedicates the whole of the eighth day to the divine motherhood--in the old rite in the content of the prayers and in the new rite in name as well as content.  Our Lady's conceiving and carrying of God the Son in her virginal womb are remembered throughout Advent, especially during the week of the O antiphons and, in the novus ordo Missae, on the fourth Sunday.
The Immaculate Conception is celebrated on the eighth of December as the first, preredemptive flowering of the grace for whose restoration Christ was born and crucified in the flesh. In the liturgical books of the Greek Church, the Mother of God is seemingly omnipresent on every day of the liturgical year,  but during the twelve days of Christmas, she receives special honours in canticles of outstanding praise, and on the second day she has a feast all of her own, the Synaxis of the Most Holy Theotokos, instituted after the Council of Ephesus in 431. On this second day of the Byzantine Christmas, the Mother of God appears before the Church as the Mystical Vine carrying in the branches of her arms 'the bunch of grapes that was never husbanded'. In the ecstasy of love she sings to her Child, 'Thou art my fruit, thou art my life; from thee have I learned that I remain what I was. Thou art my God: for seeing the seal of my virginity unbroken, I proclaim thee to be the unchangeable Word, now made incarnate.' 
 Fifth responsory.
 In the novus ordo of the West, the first of January is called the 'Solemnity of Mary; the Mother of God'. In the Missal of 1962 it is called, as it had been for many centuries, the 'Circumcision of Our Lord' because of the passage read as the Gospel. However, both the Collect and the Postcommunion place most emphasis on the divine motherhood of our Lady.
 See S. Eustratiadès, Theotokarion (Chennevières-sur-Marne, 1931), and J. Ledit, Marie dans la liturgie de Byzance (Paris, 1976).
 Menaion, p. 292.
Second excerpt, from Chapter 3, "Mother and Maiden":
As Mother of God, our Lady is without equal, surpassing by far all other created persons, whether angels or men.  After the human nature of the Son, no created entity is closer to the Trinity. According to St Thomas, Gabriel's words at the Annunciation, 'The Lord is with thee', express his recognition that the Jewish maiden is closer than he or any other angel is to the Three-Personed God:
She surpasses the angels in her familiarity with God. The angel indicated this when he said, 'The Lord is with thee', as if to say, 'I therefore show thee reverence, because thou art more familiar with God than I am, for the Lord is with thee. The Lord, the Father, is with thee, because thou and He have the same Son, something no angel or any other creature has. "And therefore the Holy which shall be born of thee shall be called the Son of God" (Lk 1: 35). The Lord, the Son, is with thee, in thy womb. "Rejoice and praise 0 thou habitation of Zion, for great is He that is in the midst of thee, the Holy One of Israel" (Is 12:6).' The Lord is therefore with the Blessed Virgin in a different way than He is with the angel, for He is with her as Son, but with the angel as Lord. 'The Lord, the Holy Spirit, is with thee, as in a temple.' Hence she is called 'the temple of the Lord', 'the sanctuary of the Holy Spirit', because she conceived by the Holy Spirit. 'The Holy Spirit shall come upon thee' (Lk 1:35). In this way, therefore. the Blessed Virgin is more familiar with God than the angel is, for the Lord Father, the Lord Son, the Lord Holy Spirit are with her, in other words, the whole Trinity. That is why we sing of her: 'Noble resting-place of the whole Trinity'. 
Our Lady is without compare in her objective dignity, and so it is fitting that she should be unrivalled in her subjective sanctity. To prepare her for the task of being Mother to the Son, both physically and spiritually, God the Father bestows upon her an incomparable plenitude of sanctifying grace, the, infused virtues and the Gifts of the Holy Spirit.