People can't get over Pippa Middleton's post-baby body after she wears bikini just 11 weeks after giving birth

Pippa Middleton documented her pregnancy workouts in a fitness column for Britain’s Waitrose magazine, and it looks as though her efforts have paid off.

Just 11 weeks after giving birth to her first son, Arthur, on Oct. 15, Kate Middleton‘s younger sister is showing off her toned and trimmed figure on a St. Barts getaway with husband James Matthews, brother James Middleton and other (non-royal) relatives.

The 35-year-old new mom appeared to have her pre-baby body back as she hit the beach in a white bikini with blue crochet detailing by Biondi.

Middleton wore a white Biondi bikini as she joined husband James Matthews for a dip in the ocean. (Photo: Backgrid)

While many moms have been candid about struggling to regain their shape after having a baby, Middleton’s athletic genes and passion for fitness may have given her an edge.

“Sport and exercise has always formed part of my daily life, from gym sessions to weekend runs, ambles or training for an event,” she wrote in a column about pregnancy workouts. “Fitness gives me energy and helps clear my mind. I love the endorphins and the buzz factor that exercise gives.”

According to Middleton’s columns, she worked out three to four times a week, enjoying cycling, swimming, tennis and classes like yoga and Barrecore.

Even so, her post-baby transformation has many people stunned.

“She just had a baby two months ago?” an Instagram commenter wrote. “Holy s***!!”

“OMG her body is amazing after giving birth,” read another comment, while one Twitter user called it “depressing for the rest of us.”

Pippa Middleton gave birth to her son in October. (Photo: Backgrid)

“I think three months is fine if you were skinny before and have a personal trainer and a chef to make your post-babe healthy meals,” remarked another Instagrammer. 

Others say the postpartum makeover is all in the genes, with one commenter dubbing it the “Middleton secret.”

“Middleton ladies have very good figures after they give birth,” added another poster, noting Kate’s own slim figure after three kids.

Read more from Yahoo Lifestyle:

Follow us on Instagram, Facebook and Twitter for nonstop inspiration delivered fresh to your feed, every day.