Called in the Gospels "the mother of Jesus", Mary is acclaimed by Elizabeth, at the prompting of the Spirit and even before the birth of her son, as "the mother of my Lord". In fact, the One whom she conceived as man by the Holy Spirit, who truly became her Son according to the flesh, was none other than the Father's eternal Son, the second person of the Holy Trinity. Hence the Church confesses that Mary is truly "Mother of God" (Theotokos). CCC 495
In today's reading, the Catechism speaks about the virginal birth of Christ and the perpetual virginity of Blessed Mary. The conception of Jesus in the Virgin Mary and His birth were supernatural acts of God. They are beliefs which brought ridicule upon the nascent Church by pagans, and scoffing by heretics who held to a more carnal view of how He was conceived inside the Virgin Mary. Yet the Gospels attest to this belief (e.g. Luke 1:26-38) and the early Church strongly upheld it. As the Catechism Companion, Vol I notes: This conception "surpasses all human understanding and possibility" (CCC 497). There has often been a misunderstanding of - and even opposition to - the miraculous conception of Jesus. Yet it was recounted by the apostles because it was true (see CCC 498). The three greatest events in the history of humanity were "worthy of proclamation" but "accomplished in God's silence": Mary's virginal conception of Jesus, the birth of Jesus, and Jesus' suffering and death on the cross. (p. 146)
The second part of this is Mary as Aeiparthenos or "Ever-virgin" (CCC 499). The perpetual virginity of the Theotokos is a belief strongly held since the early Church, confessed by the Church Fathers and is found in the Eucharistic liturgy both East and West. The Catechism notes:
Against this doctrine the objection is sometimes raised that the Bible mentions brothers and sisters of Jesus. The Church has always understood these passages as not referring to other children of the Virgin Mary. In fact James and Joseph, "brothers of Jesus", are the sons of another Mary, a disciple of Christ, whom St. Matthew significantly calls "the other Mary". They are close relations of Jesus, according to an Old Testament expression. CCC 500
In the East, some hold to these others as being half-siblings, that is children of St. Joseph from an earlier, previous marriage which seems to come from the early 2nd century apocryphal work the Protoevanglium of James. Whichever is historically correct, belief in the perpetual virginity of the Theotokos is an early and strong belief in the Church.
Finally, the Catechism speaks of Jesus entrusting Mary to all of us as our spiritual mother. As noted in CCC 501:
Jesus is Mary's only son, but her spiritual motherhood extends to all men whom indeed he came to save: "The Son whom she brought forth is he whom God placed as the first-born among many brethren, that is, the faithful in whose generation and formation she co-operates with a mother's love."
This is one of my favorite icons (click image) not only for the holy personages it portrays, but it strikes me as having a very pro-life message: St. John the Baptist in St. Elizabeth's womb "leaped for joy" when the Theotokos with Christ inside her came to visit. Even in the womb unborn children were leaping for the coming of Christ. I highly recommend this one!