The hard-working Kate, 31, is determined to crack a bottle of bubbly over a new passenger liner’s hull on June 13, a month before her July 13 due date.
The Royal Marines Band and the pipers of the Irish Guards will perform as she christens Princess Cruises’ 3,600-passenger Royal Princess in Southampton before taking maternity leave.
The ceremony will mark a break in Kate’s working life and echoes her first official engagement with husband Prince William, 30.
In February 2011, two months before their wedding, hundreds of people saw the couple dedicate a new lifeboat at Trearddur Bay, near helicopter rescue pilot William’s Anglesey base.
Since then Kate, who had worked as a website designer and photographer at her family business Party Pieces, has travelled around the world on royal duties, including to the US, Europe and Singapore.
She had to take time off in December after being admitted to hospital with severe morning sickness but then resumed her engagements. Last month she visited the Harry Potter studios in Hertfordshire, became patron to three charities and made a TV appearance.
A royal source said: “Kate has really enjoyed her job and wanted to work as close to the birth date as possible.
“The cruise ship christening on June 13 will be her last official solo engagement.”
The baby means the couple are unlikely to carry out another tour together until 2014. And Kate wants to focus on being a mum before she returns to her public duties.
The source said: “She takes her royal role very seriously and is looking forward to taking up her duties when her maternity leave has finished.”
The Prince and Princess of Wales took the infant William with them on their first tour after his birth and the Duke and Duchess of Cambridge are likely to do the same.
Earlier this month we told how Prince Harry, 28, had let slip to his friends that they are expecting a boy.
And Kate has admitted both her and Wills have plenty of things to do before the highly anticipated arrival.
They have already decorated a nursery for the youngster and Kate said: “Apparently babies have their own agenda and we have got a lot to do.”