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Creed › … › Paragraph 2. "Conceived by the Power of the Holy Spirit and Born of the Virgin Mary"
Mary - "ever-virgin"
The deepening of faith in the virginal motherhood led the Church to confess Mary's real and perpetual virginity even in the act of giving birth to the Son of God made man. In fact, Christ's birth "did not diminish his mother's virginal integrity but sanctified it." and so the liturgy of the Church celebrates Mary as Aeiparthenos, the "Ever-virgin".
Source: Catechism of the Catholic Church (Vatican.va)