Mary's motherhood and the Church's motherhood are similar and closely related:
"The Church... brings forth to a new and immortal life the sons who are born to her in baptism, conceived of the Holy Spirit and born of God" (LG VIII, 64).
The sons of the Church are conceived of the Holy Spirit as in the Incarnation of Christ. They are born of God (cf. Jn 1: 12-13).
The Church's responsibility, "by receiving the word of God in faith" (LG VIII, 64) imitates that of Mary who "received the Word of God in her heart and in her body" (LG VIII, 53).
The Church "justly looks to her, who, conceived of the Holy Spirit, brought forth Christ, who was born of the Virgin that through the Church He may be born and may increase in the hearts of the faithful also" (LG VIII, 65).