The monarch was due to return to London on Monday before a busy schedule of events including a meeting with U.S. President Donald Trump on Friday at her Windsor Castle home.
What will Prince Louis wear?
Princess Charlotte, teach us your waving technique!
The UK's Press Association said the decision is understood not to have been taken for health reasons and was mutually agreed by the Queen and Louis' parents, the Duke and Duchess of Cambridge, some time ago.
Kensington Palace announced three godfathers and three godmothers for the baby prince, including Harry Aubrey-Fletcher, The Lady Laura Meade, Mrs. Robert Carter - Hannah Gillingham - and Lucy Middleton.
Little Louis could be seen sleeping soundly in his mother's arms, despite the loud flashing cameras nearby, as Kate strolled into the chapel wearing a white long-sleeved dress with matching fascinator. Her woven Jane Taylor hat had a large flower and netting on one side.
Expected to be in attendance at the christening are Prince Charles and Duchess Camilla, Duchess Meghan Markle and Prince Harry, the Middleton family, and all of the godparents and their spouses. Pippa's husband James looked dapper in a smart suit and tie.
The Duke and Duchess of Cambridge chose hymns O Jesus, I Have Promised and Lord of All Hopefulness for the ceremony.
They also chose two anthems for the choir to sing - This is the Day which the Lord hath Made, written for their wedding in 2011 by John Rutter, and Suo Gan, a traditional Welsh lullaby.
Louis will wear the handmade replica of the Royal Christening Robe, which in 2008 replaced the original which had been worn for all royal christenings since that of Queen Victoria's eldest daughter in 1841. The new version was made by the Queen's dresser, Angela Kelly.
According to tradition, water from the River Jordan was used at the christening.
Following the service, The Duke and Duchess of Cambridge are set to give a private tea at Clarence House.
Anwar Hussein via Getty Images The Duke and Duchess of Cambridge leave St. Mary's Hospital with newborn Prince Louis on April 23, 2018.