Middleton was seen walking in the city with her phone to her ear as she ran her errands, looking casual and collected in the summer weather.
In photos seen here, the 34-year-old wore a pink-and-white striped sundress, her baby bump clearly visible. Middleton accessorized with a brown fringed leather shoulder bag, flat brown sandals and a pair of round sunglasses.
The expectant mom confirmed her pregnancy earlier this month in her column for Waitrose Kitchen magazine, revealing that her journey to becoming a mom has been quite different than sister Kate Middleton's.
Kate notably suffered from Hyperemesis Gravidarum, a severe form of morning sickness that affected the Duchess of Cambridge during all three of her pregnancies.
"I was lucky to pass the 12-week scan without suffering from morning sickness. That meant I was able to carry on as normal," Pippa wrote, according to Hello! magazine.
Hyperemesis Gravidarum can cause persistent vomiting which can lead to dehydration and weight loss, as well as severe nausea. Kate's illness caused her to miss royal appearances and spend time on bed rest, especially during the first months of her pregnancies.
Pippa, on the other hand, was able to continue as normal, though she shared that she has changed her fitness routine a bit.
"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," she wrote, adding that she kept her pregnancy a secret from her gym instructor until the "riskier" months had passed.
A source said that Kate "couldn't have been more delighted" to learn of Pippa's pregnancy and that the Duchess was the first person after Matthews to hear the news.
"When Pippa found out she was pregnant, she was obviously thrilled and utterly overjoyed," the source said. "Naturally, big sister Kate and parents, Carole and Michael, were the first people she told — James aside — and they could not have been more delighted."
"Pippa and James have always known they wanted children," the source added. "They have made the most of their first few months of marriage and felt the time was right to expand their family."
Pippa is reportedly due in October.
Photo Credit: Getty / Max Mumby/Indigo