Kate Middleton celebrates her final birthday as a commoner on Sunday - turning 29 less than four months before she marries Prince William.
Celebrations are expected to be low key as Miss Middleton continues finalising arrangements ahead of her and William's big day on April 29.
Clarence House would not release details of Miss Middleton's plans for
Sunday - simply saying she would be spending her birthday "privately".
One royal commentator said the former accessories buyer for fashion chain Jigsaw was about to enter an extremely busy party season, so might prefer quieter celebrations with her parents and siblings James and Philippa.
Ingrid Seward, editor of Majesty magazine, said: "I think she could be with her family as they'll be wanting to do something as it's her last birthday as their little girl - I suspect at the family home.
"There are a lot of parties coming up so she might just want some really, really close friends and family with her - or it could be just her and William.
"I would think no woman looks forward to being 29 and getting close to 30.
"It's not the biggest birthday celebration.
"If I was her mum, I would be giving her a really lovely dinner party, something really beautiful with her brother and sister there.
"She will probably want to keep a low profile because the rest of her life will be high profile."
This time next year Miss Middleton, who met Prince William while they studied at St Andrews University, will be looking forward to her 30th birthday as an ennobled member of the Royal Family.
If William takes on a dukedom on April 29, most likely becoming the Duke of Clarence, Duke of Cambridge, Duke of Connaught or the Duke of Sussex, she will become a Duchess.
However, if the Prince surprises everyone and turns down a title, his new wife will become HRH Princess William of Wales, Princess Catherine or Kate of Wales.
Regardless, on Sunday she will be trying to take good care of the
birthday gifts she receives.
Last year, it was reported that Otto, her pet cocker spaniel, ate a
pair of pearl earrings William gave her.
The dog apparently took them from an ornamental dish at the side of her bed and left tooth marks in a tube of handcream.
A wait for nature to take its course was required before the antique jewellery resurfaced.
The year before, Miss Middleton celebrated her 27th birthday as bookies halved their odds on the couple announcing their engagement that year.
It was not money well spent.
The bookmakers slashed their odds after the pair spent much of the festive break holidaying at the royal retreat of Birkhall, the Prince of Wales's home on the Queen's private Balmoral estate in Scotland.
Twelve months earlier, the history of art graduate marked her 26th birthday with a house party before dinner at a Chelsea restaurant and finished the night partying at a Sloane Square nightclub.
Yesterday, the couple released new information about their eagerly awaited wedding.
They revealed the bride-to-be's route to Westminster Abbey and confirmed that Archbishop of Canterbury Rowan Williams will marry them.
Breaking convention with the biggest royal weddings of recent memory,
Miss Middleton will travel to the ceremony by car.
There is no royal protocol stating a bride-to-be must travel by horse-drawn carriage. The decision is up to the woman.
But in 1981 Diana Spencer travelled to marry Prince Charles at St Paul's Cathedral by glass coach, as did Sarah Ferguson in 1986 when she married Prince Andrew at the Abbey.
But in 1999 Sophie Rhys-Jones travelled by car for her wedding to Prince Edward at St George's Chapel in Windsor Castle.
William and Miss Middleton's service, which will began at 11am, will be watched by billions and conducted by the Dean of Westminster, the Very Rev Dr John Hall.
Afterwards, the Queen will hold a reception at Buckingham Palace and the Prince of Wales will give a private dinner, followed by dancing in the evening, for the couple and their close friends and family.