Youcat commented through CCC - Question n. 80 - Part I.

YOUCAT Question n. 80 - Part I. Why is Mary a Virgin?

(Youcat answer) God willed that Jesus Christ should have a true human mother but only God himself as his Father, because he wanted to make a new beginning that could be credited to him alone and not to earthly forces.       

A deepening through CCC

(CCC 484) The Annunciation to Mary inaugurates "the fullness of time" (Gal 4:4), the time of the fulfillment of God's promises and preparations. Mary was invited to conceive him in whom the "whole fullness of deity" would dwell "bodily" (Col 2:9). The divine response to her question, "How can this be, since I know not man?", was given by the power of the Spirit: "The Holy Spirit will come upon you” (Lk 1:34-35 Gk.). (CCC 485) The mission of the Holy Spirit is always conjoined and ordered to that of the Son (Cf. Jn 16:14-15). The Holy Spirit, "the Lord, the giver of Life", is sent to sanctify the womb of the Virgin Mary and divinely fecundate it, causing her to conceive the eternal Son of the Father in a humanity drawn from her own.    

Reflecting and meditating 

(Youcat comment) Mary’s virginity is not some outdated mythological notion but rather fundamental to the life of Jesus. He was born of a woman but had no human father. Jesus Christ is a new beginning in the world that has been instituted from on high. In the Gospel of Luke, Mary asks the angel, “How can this be, since I have no husband?” ( do not sleep with a man, Lk 1:34); the angel answered, “The Holy Spirit will come upon you” (Lk 1:35). Although the Church from the earliest days was mocked on account of her belief in Mary’s virginity, she has always believed that her virginity is real and not merely symbolic.

(CCC Comment)

(CCC 486) The Father's only Son, conceived as man in the womb of the Virgin Mary, is "Christ", that is to say, anointed by the Holy Spirit, from the beginning of his human existence, though the manifestation of this fact takes place only progressively: to the shepherds, to the magi, to John the Baptist, to the disciples (Cf. Mt 1:20; 2:1-12; Lk 1:35; 2:8-20; Jn 1:31-34; 2:11). Thus the whole life of Jesus Christ will make manifest "how God anointed Jesus of Nazareth with the Holy Spirit and with power" (Acts 10:38).     

(This question: Why is Mary a Virgin?  is continued)