The phrase "in the manger" was deleted in the second and all subsequent Urantia Foundation printings, leaving the sentence: "These men of God visited the newborn child." Presumably, this change was made because according to 122:8.1 -7, three wise men from the east visited Jesus when he was almost three weeks old, after the family had moved out of the stable and perhaps after they had left the inn.
The text has been restored to its original form in this edition because it is certainly possible that Joseph and Mary might have taken the manger with them up to the room in the inn in order to continue to have a cradle for Jesus. The need for a cradle would have been no less in the inn than in the stable, and if the manger was portable, moving it along with the family seems quite reasonable.
Original Paragraph:
P1317:2, 119:7.6 Certain wise men of earth knew of Michael's impending arrival. Through the contacts of one world with another, these wise men of spiritual insight learned of the forthcoming bestowal of Michael on Urantia. And the seraphim did, through the midway creatures, make announcement to a group of Chaldean priests whose leader was Ardnon. These men of God visited the newborn child in the manger. The only supernatural event associated with the birth of Jesus was this announcement to Ardnon and his associates by the seraphim of former attachment to Adam and Eve in the first garden.