It dramatises the dilemmas faced by the young Joseph and Mary after the latter became pregnant out of wedlock. And in a case of life imitating art, the star of Catherine Hardwicke's The Nativity Story is also finding her own impending motherhood to be a source of woe.

According to reports, Pope Benedict XVI is to boycott this weekend's Vatican premiere of Hardwicke's retelling of the events leading up to the virgin birth because 16-year-old Keisha Castle-Hughes, who plays Mary, has herself become pregnant outside of marriage.

The new film from the director of Thirteen and Lords of Dogtown had been expected to receive the Pope's blessing at the special screening, but it is understood the Catholic church disapproved of Castle-Hughes' "situation".

However a spokesperson for the Vatican said the Pontiff had previously committed to another function in Turkey and would never have been able to attend the premiere. "The surprise would have been if he had [attended]," the spokesperson added.

Hardwicke is due to arrive alongside fellow cast member Shohreh Aghdashloo. The event will serve as a benefit, with contributions going towards the construction of a school not far from the town of Nazareth in Israel, where the film's story is set.