It reads:
God our creator,
we thank you for the wonder of new life
and for the mystery of human love.
We pray for William, Duke of Cambridge and Catherine, Duchess of Cambridge
as they prepare to receive the gift of their child.
We thank you that we are known to you by name
and loved by you from all eternity,
through Jesus Christ our Lord. Amen
The Duchess was admitted to the King Edward VII hospital this week suffering from acute morning sickness, and is being given extra fluids and nutrition.
She is expected to remain in hospital for several days.
It is reported that the couple had not intended to go public with news of her pregnancy before the 12-week stage but decided to announce it when she was admitted to hospital.
A spokesman for St James's Palace said: "Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting a baby.
"The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall and Prince Harry and members of both families are delighted with the news."