§505
Creed › … › Paragraph 2. "Conceived by the Power of the Holy Spirit and Born of the Virgin Mary"
Mary's virginal motherhood in God's plan
By his virginal conception, Jesus, the New Adam, ushers in the new birth of children adopted in the Holy Spirit through faith. "How can this be?" Participation in the divine life arises "not of blood nor of the will of the flesh nor of the will of man, but of God". The acceptance of this life is virginal because it is entirely the Spirit's gift to man. The spousal character of the human vocation in relation to God is fulfilled perfectly in Mary's virginal motherhood.
Source: Catechism of the Catholic Church (Vatican.va)