"I'll take it!" she said, after a big laugh.
She was named as a patron of Mayhew, based in north west London, last week, one of four patronages announced at the time, reflecting her interest in supporting the arts, vulnerable women and education.
Meghan's four patronages "reflect the causes and issues with which she has always been associated including the arts, access to education, support for women and animal welfare", Kensington Palace said in a statement last week.
ITV News royal editor Chris Ship reported via Twitter on Monday that Markle told one woman in the crowd while visiting the English town of Birkenhead with Prince Harry that she is 6 months pregnant, and told another woman the due date is around April.
Meghan The Duchess of Sussex arrives at the Mayhew animal welfare charity on Wednesday, wearing a cheap maternity dress.
- Kensington Palace (@KensingtonRoyal)At @TheMayhew The Duchess of Sussex meets Wully, a formerly homeless Pet Refuge service user, and his two dogs Azzy and Gallis - Wully was helped by Mayhew's Animal Welfare Officers.
The navy boatneck "Sarandon" dress, with its long sleeves and knee-high slit, perfectly hugged Meghan's growing baby bump as she met Cirque officials and made her way into Royal Albert Hall.
Holding Maggie, who was brought to the Mayhew in November after her owner was unable to care for her, the Duchess said: "We can't get another dog before the baby, our hands are full". Meghan, 37, wore her raven hair neatly up and sported smokey eye makeup, flushed cheeks and nude, glossy lips.