Royals Pippa Middleton Revealed the Secret to Her Post-Baby Bikini Abs Pippa Middleton's post-baby bikini body was nine months in the making! By Erin Hill Erin Hill Twitter Senior News Editor, PEOPLE People Editorial Guidelines Published on January 3, 2019 10:59 AM Share Tweet Pin Email Pippa Middleton’s post-baby bikini body was nine months in the making! The 35-year-old first time mom, who welcomed son Authur in October, is famously athletic. From grueling marathons to downhill ski races, the younger sister of Kate Middleton has kept up a tireless workout routine. And her dedication to fitness continued throughout her pregnancy. “When I learned the happy news that I was pregnant, I realized I needed to adjust my four to five-day-a-week [fitness] routine,” Pippa wrote in her column for the U.K. supermarket monthly Waitrose Kitchen magazine, noting that she kept her pregnancy a secret from her gym instructor until the “riskier months” were over. Eliotpress/MEGA “This being my first pregnancy, I had so many questions I felt were still unanswered,” Pippa said. “I wanted to know things like, would I strain if I served in tennis, are strokes of swimming safe, can I still do a normal yoga class if I avoided certain positions? Could I still work my abs?” Eliotpress/MEGA Pippa said she continued to swim, play tennis and keep up with her barre workouts during her pregnancy. Everything New Mom Pippa Middleton Has Said About Her First Pregnancy “It’s comforting to know that [swimming] is safe throughout pregnancy, and you don’t need to adapt and change too much (unlike most other sports). It’s so good for you that you could swim every day – as long as you don’t overexert yourself – right up until the end of the third trimester,” she wrote. When it came to tennis, she said she was told to “keep two feet on the ground when hitting strokes and to avoid sharp turns and quick movements, particularly as I approach the due date.” She added that barre workouts are “excellent for pregnant women in all trimesters as you mostly rely on your body weight, so it means little impact for your joints and is generally low risk.” Max Mumby/Indigo/Getty “I feel far from a ballerina, but I’m equally determined not to break into a penguin-style waddle and plod around with bad posture,” she continued. First-Time Aunt Kate Middleton Reacts to Birth of Nephew — 6 Months After Welcoming Prince Louis “I’ve noticed my body change and weight increase, but through effective exercise and sports I feel that it’s been strengthened to support a healthy pregnancy, birth and recovery . . . And ensure that post-baby, my old favorite jeans will still fit eventually!” In addition to those jeans, she was also able to slip back into her pre-baby bikini. Just 10 weeks after giving birth, the new mom was spotted in a white two-piece with black stitching on Wednesday in St. Barts with husband James Matthews. The couple walked along the shore hand-in-hand and also enjoyed a dip in the water together.