If Jesus was God, and Mary was his mother, then that made her the Mother of God. The first Christians called Mary the “Mother of God” without hesitation. There was scriptural precedent, and it seemed logical.
Mary's mothership of God is a dogma of the Catholic Church. Scriptural basis for the dogma is found in John 1:14 which states "And the Word became flesh, and dwelt among us" and in Galatians 4:4 which states "God sent forth his Son, born of a woman, born under the law".
Isaiah 7.14 talks about a Virgin who would conceived and bear a son and shall call his name Immanuel which means God is with you, so if God is With us, what do we call the woman who carried or bore that Son who was God himself?. That Woman is now called the Mother of God who was with us in the Flesh.
John 1.1 to 14 talks about God's fleshly manifestation saying " In the beginning was the word and the word was with God and " the word was God" and the word was made Flesh and dwelt among us. Take note the middle part of these words which say " And the word was God". Next, let's examine Mary's role. So, if that word who was with God and was God himself and dwelt with us in his Human Deity nature, what do we call the Woman who bore/carried that God who manifested in the flesh? none other than the Mother of God Himself.