Immaculate Mary, Matchless in Grace | John Saward | Two excerpts from Cradle 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.'