We celebrate the feast of the Annunciation and thus the beginning of Mary's pregnancy on March 25, nine months before Christmas, so it may surprise you that in December we return three times to the various annunciations of Jesus' birth.
And it is important to note that all these annunciations were also moments of vocation. God announces his plan, and this has implications for the recipient personally, their role in his plan.
For instance, on today's feast of the Immaculate Conception, on which — by the way — we celebrate Mary's conception by her mother, we have the first half of Luke's version of the annunciation of Jesus' conception by Mary. The angel Gabriel appears to Mary and gives us the first sentence of what is now the Hail Mary in the words he uses to invite her to accept her God-given vocation, her role in God's plan: "Hail Mary, full of grace, the Lord is with thee,” a greeting which we now repeat as the first sentence of the most widely prayed prayer in the world, to which Mary responds: "Behold, I am the handmaid of the Lord. May it be done to me according to your word" — thereby opening her heart to welcome God's call in her life, her vocation, even though she really didn't know what she was getting into.
“But Mary didn’t have to know everything; she was a woman of faith. For a faithful servant, the answer when God calls is always ’Yes!’”