The angel Gabriel announces to the virgin Mary that she is to be the mother of the Messiah. Nothing is impossible for God. Mary is taken by surprise. She wasn’t planning on this. She was engaged to be married. In hindsight, it is pretty obvious that the Mother of Our Lord needed to be married. She would need a husband to raise the Messiah. The Messiah would need an earthly father in order to be properly protected, provided for, and educated.
I don’t think that is what we usually think about when we hear that the virgin will conceive and bear a Son. We don’t think about her being married or the Messiah’s need for an earthly father. We focus on the miracle of conception within virginity. Perhaps this was also the way Mary had thought about the prophecy of the virgin conceiving and bearing Immanuel.