The young royal couple have become global stars after some two billion people tuned in to watch their glittering marriage ceremony and the sumptuous display of pageantry that accompanied it, and barely a day goes by without a picture of Catherine appearing in the pages of Britain's royalty-obsessed newspapers.

The duchess, the first "commoner" to marry a prince in close proximity to the throne in more than 350 years, is now a fashion icon, with her attire scrutinised every time she steps out in public and followed by legions of women around the world.

Britain's Prince William and his fiancee Kate Middleton are seen smiling as they attend a Naming Ceremony and Service of Dedication for the Royal National Lifeboat Institution's (RNLI) new Atlantic 85 Lifeboat, the 'Hereford Endeavour', at Trearddur Bay Lifeboat Station, in Trearddur Bay, Anglesey in north Wales February in this 24, 2011 file photograph. [Photo/Agencies]

US President Barack Obama and his wife Michelle were one of the first to send congratulations, an indication of the young royals' popularity across the Atlantic.

"I know they both feel that having a child is one of the most wonderful parts of their lives. So I'm sure that will be the same for the Duke and Duchess of Cambridge," said White House spokesman Jay Carney.

With their fame has come unwanted attention, and there was anger in Britain when topless photos of Kate relaxing on holiday were published in a French magazine in September.

The pictures rekindled memories of the media pursuit of William's mother, Princess Diana, who was killed in a car crash in Paris in 1997 while being chased by paparazzi.

"I will be very surprised if this isn't handled with the utmost tact and sensitivity," said media commentator Steve Hewlett. "Newspapers realise there's a huge amount of goodwill towards Will and Kate, and they take their cue from their readers."

"DADDY'S LITTLE CO-PILOT"

Kate made her last public appearance on Friday when she returned to her old school - a minor event that nonetheless generated live television coverage on news channels - when she looked healthy and joined in a game of hockey with pupils.

Earlier in the week William had hinted at a pregnancy during a visit to Cambridge in central England when they were given a home-made baby suit emblazoned with the words "Daddy's little co-pilot", a reference to William's job.

"When I gave it to him he said 'I'll keep that', and handed it to his aide," said Samantha Hill.

Joseph, author of "Kate: The Making of a Princess", said she believed the couple, who currently live in north Wales where the prince is based as a search and rescue pilot, had been waiting for the right moment to have a baby.

"My feeling has always been that they were not going to take the spotlight away from the queen in her Jubilee. But now 2013 is going to be William and Kate's year," she said, adding the couple would make wonderful parents.

"We have seen her with children and she is lovely with them, she's got the natural touch, and her parents run a party business and she has spent a lot of time with children," Joseph said. "(William) he has always talked about wanting children, so I am sure he is delighted."