The 37-year-old author appeared in posts on Instagram and Twitter sporting a red festive jumper after she presented awards to Mary Hare School for deaf children and young people. The jumper’s Christmas tree design synchronises with a tastefully decorated tree in the picture’s backdrop, which appeared to be taken in her London home.
Ms Middleton presented awards to pupils at the Berkshire school for their best Christmas card designs, appearing via Zoom.
It comes amid reports she is expecting her second child with husband James Matthews, 45, a hedge fund billionaire.
The couple live in a six-bedroom home in Chelsea, believed to be worth £17million.
Pippa spent last Christmas on the beach in St. Barths with James and her mom, Carole.
The photo, posted at the weekend, is captioned: “Pippa Middleton (our ambassador) joined the pupils on Zoom today, to present the awards for the Christmas card designs.
“Well done to all our primary and secondary pupils who received awards and joined in the spirit of Christmas jumper day!”
The younger sister of the Duchess of Cambridge has a two-year-old son named Arthur.
Pippa’s second baby will also be a first cousin of Prince George, seven, Princess Charlotte, five, and Prince Louis, two.
READ MORE: Kate Middleton & ‘pregnant’ sister Pippa may spend Christmas apart
Her father-in-law, David Matthews, is Laird of Glen Affric, a 10,000-acre estate in the Scottish Highlands.
James will inherit the title from his father, meaning Pippa will become Lady Glen Affric.
James Middleton, 33, Kate and Pippa’s younger brother, took a host job at the exclusive property.
Kate, 38, and her sister are known to share a close bond.
Pippa has spoken about their relationship publicly, revealing that nothing changed when Kate joined the Royal Family.
In a 2014 interview with NBC’s Today programme, she said in response to this question: “Not particularly, no. I mean, obviously she has pressures that she’s taken on and things.
“But we spend a lot of time together. We still do a lot together as a family.
“And I think that’s really the heart for all of us is having a really close family that we can sort of be normal with each other, treat each other normally.
“And that’s sort of kept us all, you know, affixed to the ground.”