The 29-year-old refused a sample of peanut paste from a UNICEF aid package during a trip to a distribution centre in Copenhagen, prompting rumours that she was following health advice handed down to expectant mothers. Pregnant women are advised against eating peanuts to prevent allergies developing in their babies.
Tabloid reports in the US add that Middleton gave her husband a "knowing look" as she declined to taste the sample.
ABC News further claimed that Buckingham Palace "went out of their way to stress that [Middleton] has no nut allergy whatsoever".
A spokesperson for the Duke and Duchess of Cambridge has refused to comment on the pregnancy rumours.
Prince William and Middleton chose to visit the Denmark UNICEF centre in order to raise awareness of the famine crisis in East Africa.
Snoop Dogg this summer offered to create some "baby-making" music for the royal couple.