A spokeswoman for Pippa and her husband James Matthews said the baby was born on Monday and weighed 8lb and 9oz.
The birth comes one day after it was revealed Harry and Meghan, the Duke and Duchess of Sussex, were expecting their first chid.
The 35-year-old announced she was pregnant with her first child in June.
"She swam parallel to the beach for about 100-130 feet, doing both the front crawl and backstroke". In her most recent column, Pippa wrote about the discomfort of her final weeks.
Still, the couple had enough time to attend Princess Eugenie's wedding before checking in to the hospital just three days later.
Patients are given private rooms with their own en suites while gourmet food is available.
Pippa and James were married in May 2017 after dating for almost a year. Understandably so, as a deluxe room in the wing will set you back more than $12,000 for the first night.