The Duchess of Cambridge has joked she and her husband should have another baby, after being given a present designed for newborns.
The Duchess, already a mother-of-two, was offered a cuddly toy designed to soothe tiny babies during an event for start-up tech companies on Monday.
Saying thank you for the present, she turned to the Duke laughing and said: "We will just have to have more babies."
The soft toys, from company Whisbear, are designed to comfort newborns by replicating the sound of the womb, responding to their cries to soothe them.
Julia Sielicka-Jastrzebska, who founded the company with her sister, said the Duchess made the light-hearted comment after learning the bears, which she had admired, were designed for children younger than George and Charlotte.
"We gave the Duchess some presents for Prince George and Princess Charlotte," she said. "She said they should have more babies, and they laughed."
Among the presents were a bear for each child, and a t-shirt for the Duchess with the slogan "i'mperfect"; part of the company's campaign to encourage mothers not to feel the pressure to be flawless.
The Duke and Duchess were at The Heart, an incubator for digital and tech start-ups in Warsaw.
The Royal couple were shown a variety of innovations, including a robot designed for children to code and a fetal heart monitor to allow pregnant women to track their health at home.
The Duke and Duchess both tried on virtual reality headsets showing them a view of Warsaw and played with a robot by company Proton which moved when the Duchess patted its head.
Before taking their leave, the Duke and Duchess spent time with six Polish students who are studying in the U.K.
Asked for a selfie with three of them at the end, the Duke laughed "I'm allergic to selfies but let's take a photograph".
Watching his wife pose with the others, he made her laugh by teasing her: "You don't look as clever as the other three."
Finally, the Royal couple presented Whisbear with the HealthTech Startup Award, giving a second award for "omnichannel startup" to Migam, which helps deaf people accessing services by connecting them with sign language interpreters via video.
The Duke and Duchess appeared on playful form as they made their way around the digital innovations.
Meeting with a group of Polish students who study in the UK, the Duke made the Duchess giggle as she posed for a photograph, teasing her: "You don't look as clever as the other three."
The final engagement of the day saw the couple attend a garden party in honour of the Queen's birthday in the Orangery, Lazienki Park.
In a short speech, the Duke said: "We in the United Kingdom value our links with Poland enormously. "We admire Poland as a remarkable example of courage, fortitude and resilience."
He added: "With such links - diplomatic, military, cultural - offer much promise and opportunity for the future."