Even so, dressed in a favourite blue Alexander McQueen coat and with a jaunty Lock & Co hat, Kate looked glamorous - and also managed to bag a historical first.
As she attended a service in London to mark the 75th anniversary of the founding of the Air Training Corps, the duchess became the first female Honorary Air Commandant. She has taken over the position from Prince Philip.
To mark the occasion Kate wore the eye-catching diamond and ruby Dacre brooch, given to the best female cadet of the year since 1982, when girls were finally permitted to join the once all-male organisation.
The brooch was donated to the ATC by Elizabeth Dacre, whose late husband Air Commodore George Dacre was a former station commander at RAF Halton, Buckinghamshire, and who herself achieved the WAAF equivalent of Group Captain during the Second World War.
Last year it was agreed that top female cadets should receive a sword like their male counterparts, and so the brooch has been loaned to Kate to wear on official engagements.
Warrant Officer Lucinda Conder, 19, who was the last cadet to wear the brooch, said Kate told her yesterday that Prince George, two, wants to become an air cadet after seeing pictures of Spitfires.
-Daily Mail