Seven days later and there was no mistaking the swell of the Canada-born royal's midriff as she relaxed on the grass with her husband Peter at the Festival of British Eventing at Gatcombe Park.
Autumn, who was casually dressed in a summery pink t-shirt and white trousers, certainly seems to be taking her first pregnancy in her stride.
The 32-year-old – expecting the Queen's first great-grandchild – looked radiant as she laughed with her spouse on day three of the competition, held annually at the private country home of her mother-in-law, Princess Anne.
On Saturday, the happy couple, who now reside in Hong Kong, had the chance to catch up with their nearest and dearest, as the royal family stepped out in force to support Olympic equestrian hopeful, Zara Phillips.
Peter's youngest sister was competing in the competition, and her mother, father and Prince William were all there to cheer her on in absence of her long-term love, rugby star Mike Tindall, who was at an England training camp.