The Congregation for Divine Worship and the Discipline of the Sacraments recently gave a “Directory on Popular Piety and the Liturgy”, (Vatican City, 2001). The following is an excerpt taken from that document concerning Mary and Advent.
Liturgy frequently celebrates the Blessed Virgin Mary in an exemplary way during the season of Advent.
 Liturgy frequently celebrates the Blessed Virgin Mary in an exemplary way during the season of Advent. It recalls the women of the Old Testament who prefigured and prophesied her mission; it exalts her faith and the humility with which she promptly and totally submitted to God’s plan of salvation; it highlights her presence in the events of grace preceding the birth of the Savior. Popular piety also devotes particular attention to the Blessed Virgin Mary during Advent, as is evident from the many pious exercises practiced at this time, especially the novena of the Immaculate Conception and of Christmas.
However, the significance of Advent, "that time which is particularly apt for the cult of the Mother of God", is such that it cannot be represented merely as a "Marian month."
In the calendars of the eastern Churches, the period of preparation for the celebration of the manifestation (Advent) of divine salvation (Theophany) in the mysteries of Christmas-Epiphany of the Only Son of God, is markedly Marian in character. Attention is concentrated on preparation for the Lord's coming in the Deipara. For the Orientals, all Marian mysteries are Christological mysteries since they refer to the mystery of our salvation in Christ. In the Coptic rite, the Lauds of the Virgin Mary are sung to the Theotokia. Among the Syrians, Advent is referred to as the Subbara or Annunciation, so as to highlight its Marian character. The Byzantine Rite prepares for Christmas with a whole series of Marian feasts and rituals.
Congregation for Divine Worship and the Discipline of the Sacraments,
“Directory on Popular Piety and the Liturgy”, (Vatican 2001)