But when the pensioner questioned whether she really did know the sex of her unborn child Meghan added: "I don't, I promise you - no - we're going to be surprised".
One care home resident named Peggy McEachrom, who was delighted to meet Meghan, teased the Duchess about her baby bump and said: "You are such a fat lady!"
The duchess toured the charity's north-west London headquarters in Kensal Green to mark last week's announcement that she has become the organisation's patron.
Her large baby bump could really be seen in the fitted garment as she stepped out of her auto with a big smile. The Duke and Duchess of Sussex are set to attend the premiere performance of Cirque du Soleil Totem at the Royal Albert Hall on Wednesday, January 14.
The 37-year-old royal also had a laugh with the staff and visitors.
She now owns two rescue dogs - a beagle named Guy and a Labrador-Shepherd mix named Bogart, who remains in Toronto, Canada with her friends.
Meghan The Duchess of Sussex arrives at the Mayhew animal welfare charity on Wednesday Jan. 16, 2019, to meet with volunteers to hear about welfare initiatives, community engagement and global projects carried out by the charity.
It is thought Meghan researched Mayhew on the internet before approaching the charity to learn more about its work, and made two private visits, the first in November, before her public tour.
One picture showed the Duchess snuggling up next to her two dogs, Guy and Bogart, who appeared to be sleeping cosily next to Meghan.
During the visit Meghan, a keen dog lover, spoke about her own rescue dogs.