They are both pregnant and may both the subject of malicious gossip.
Elizabeth is too old to be pregnant.
Elizabeth's young cousin Mary is scarcely old enough to be pregnant.
Have Mary's parents sent her far away to the hill country of Judea on the pretext of helping old Elizabeth, but really to shield her from disgrace in Nazareth before her condition began to show? Mary is pregnant and the father is not her fiance Joseph. Who would believe her story of being visited by an angel and conceiving a child by the Holy Spirit of God?
The story of Mary's prenatal visit to Elizabeth is told in Luke 1: 39 - 56.
The reason for the joy in Elizabeth's face shown in the image at the head of this post it explained in the gospel like this:
When Elizabeth heard Mary's greeting, the child leaped in her womb. And Elizabeth was filled with the Holy Spirit and exclaimed with a loud cry, "Blessed are you among women, and blessed is the fruit of your womb. and why has this happened to me, that the mother of my Lord comes to me? For as soon as I heard the sound of your greeting, the child in my womb leaped for joy. and blessed is she who believed that there would be a fulfillment of what was spoken to her by the Lord."
That exclamation of joy is followed by Mary's Song of Praise.
It is beautifully sung here by the 'Daughters of Mary' and with some art images of the 'Visitation'. Enjoy.
(As yesterday was Trinity Sunday the Feast of 'The Visitation of the Blessed Virgin Mary to Elizabeth' which is usually 31 May is this year 2015 transferred to today 1 June.)
Image Credit: Commons Wikimedia