Therefore, we say Mary was the mother of God because 1) Jesus is the second person of the Trinity - thus God 2) Mary gave birth, nursed, raised, taught, and loved Him - thus mother 3) So Mary was the Mother of God. read more
Mother of God is not been understood, or intended to be understood, as referring to Mary as Mother of God from eternity. Catholic and Orthodox Christians understand Jesus Christ as both fully God and fully human, they call Mary Mother of God/Theotokos to affirm the fullness of God's incarnation. read more