I preached from Luke 1 today. The story of Jesus in Luke begins in barrenness. He begins his gospel with 2 miraculous births: 1) an old lady who was "out of her prime," and 2) a young teenage girl who was a virgin. God seems to enjoy working within the realms of the impossible.
However, Elizabeth and Mary aren't the only ones expecting in Luke 1, all of Israel was expecting. The beginning of Luke asks us, "Are we expecting? What are our expectations for God?"
Elizabeth and Mary aren't the only ones delivering in Luke 1. Even more so, God is delivering. He is delivering a new prophet, a new King, a new teaching, a new community...ultimately, he is delivering good news to all of humanity.
And, He is still delivering today!